Ediacaran

Palaeoporn 24

2011-10-10T14:25:00.000+11:00

Tribrachidium heraldicum

Ediacaran goes back to its roots with this Palaeoporn, with probably the most enigmatic of a group of enigmatics, Tribrachidium heraldicum.

Tribrachidium (photo credit)

Tribrachidium is a disc-shaped organism which is characterised by having three 'arms' which spiral out from the centre. Tribrachidium always occurs in negative hyporelief (pressing up into the bottom surface of the sandstone bed) indicating that it had a rigid body that pressed upwards into the overlying sand. The photo above is actually of a cast taken from a fossil so that the original body relief is shown - i.e. this is positive relief. The actual fossil is at right.

The tripartite body plan of Tribrachidium is quite unusual as most metazoans are either bilaterally or radially symmetrical.

So what is it? Well Tribrachidium is a cnidarian. Umm no, actually it's a lophophore (related to brachiopods), umm, or it could be an echinoderm, umm, no, it's an ecdysozoan (a group characterised by organisms that shed their external covering), no actually it's a sponge . . . possibly. Alternatively it could belong to a whole new phylum, the Phylum Trilobozoa. Umm, maybe Class Trilobozoa, well, clade trilobozoa anyway.

So its been a question of, "Look! Up in the sky! Is it a lophophore? Is it a cnidarian? No it's . . . , umm . . . , it's . . . , well . . . , it's a Trilobozoan! Yeah . . . , that's what it is, a Trilobozoan.

[voice from the crowd] It's a what?

Trilobozoan.

[voice from the crowd] What's a Trilobozoan?

Glad you asked.

The Trilobozoa are predominately an Ediacaran group who's members have a tripartite or tri-radial body plan, typified by Tribrachidium.

A triumvirate of Trilobozoa. Albumares Brunsae (x4) (left), Anfesta stankovski (x1) (top right) (Photo credit). Rugoconites enigmaticus (x1) (Photo credit)

The group is a bit of a grab-bag with Albumares and Anfesta from Russia and maybe Rugoconites, as well as some others. The tripartite body plan is almost unique with modern examples confined to teratological (developmental defects) causes. Like Tribrachidium, other trilobozoans are usually found in negative hyporelief and, importantly, although not common, where they do occur in groups they do not overlap, indicating that they are not 'strandings' or simply groups of free swimming forms washed together (otherwise they would overlap).

Tribrachidium, the most common and hence most studied, can also be found in size range of 3 to 30 mm indicating a growth pattern of organisms recruited to the sea floor and growing there, rather than a free swimming form where the sizes would be similar due to current activity. Trilobozans are thought, then, to have been sessile filter feeders, attached to the microbial mats, normally by a bulb-like structure, throughout adult life.

It appears as though the tripartite body plan, or derivatives of it, were quite common in the Ediacaran. Finds such as Ventogyrus are being reinterpreted as a stalked trilobozoan, but placed within the Phylum Cnidaria. Another form, Eoandromeda octobrachiata, though to be related to comb jellyfish (a group of vicious killer jellyfish), is also though to share a number of features in common with Tribrachidium.

So evidence is growing that trilobozoans may well be Cnidarian.

Vicious killer jellyfish, trilobed body plans! The Cnidaria have a lot to answer for!

Trilobozoan Cnidarians? Reconstructed. Tribrachidium stamp (left). Ventogyrus (photo credit)

3.4 Billion Year Old Microfossils? . . . Umm Yes (Probably)

2011-08-28T21:09:00.000+10:00

Sshhh, be vewy vewy quiet. We’re hunting Awchean pwokawyotes.

There is good carbon and sulphur isotope geochemical evidence that life has existed on Earth from the early Archean. This life is thought to consist of small prokaryote cells with a penchant for sulphur instead of oxygen.

However, identifying actual fossil evidence is very tricky for a number of reasons. One of the major ones being, that given the 3.5 billion year time span and plate tectonics, few rocks from this period of Earth history remain on the surface. Of those that do, most either were unsuitable to preserve life in the first place (e.g. volcanic rocks) or have been metamorphosed until any possible organic trace has been cooked to oblivion.

So, if you want to go hunting Archean microbes you need to look in an area with rocks that have been relatively unmolested for some 3.5 billion years or so.

Presenting the Pilbura Craton, Western Australia. The Craton consists of (relatively) unaltered 3.7-2.6 billion year old rocks formed of a granite–greenstone terrane consisting of a series of dome shaped granitoid bodies, overlain by an extensive sequence of Archaean and later metasediments. Within the Craton, the East Pilbara Terrane contains a suite of approx. 3.4 billion year old sedimentary rocks which occur sandwiched between two suites of volcanic rocks.

This is the Strelley Pool Formation and is thought to be between 3426-3340 million years old. At the base of Formation, sitting unconformably on underlying 3515 million year old basalts, is a remarkably well preserved sandstone. (The ridge in the header image above. The red dots mark the position of the unconformity between the underlying basalts and the Strelley Pool Formation. Image (sans Elmer) from Wacey et al. 2011. Supplementary Information)

The sandstone is dark coloured at the base, due to it being carbonaceous- and pyrite-rich, where it sometimes fills channels eroded into the underlying basalt. Above this, the sandstone becomes lighter as the carbonaceous matter and pyrite disappear, before passing into overlying limestones - which contain possible stromatolites - and cherts.

Thin section photomicrograph showing multiple generations of carbonaceous material and silica cements within the Strelley Pool sandstone. DQ, detrital quartz grains. C1, carbon material, interpreted as a biolfilm, covering quartz grains. S1, first silica cement layer, up to c. 30 μm partially filling the void space between the detrital quartz grains. C2, A second carbon biofilm covering the surface of the S1 silica layer. S2, a second generation of silica cement precipitated in the larger pore spaces. C3, a third generation of carbon biofilm. (Wacey et al. 2011. Supplementary Information).

This fantastic thin section photomicrograph provides a wealth of information that allows us to reconstruct how the sandstone was formed. The grains are well rounded detrital quartz. Grains of detrital pyrite are also present. The grains are covered with a thin film of carbonaceous matter, and show a number of silica cementation events, some of which show a dripstone texture.

A second film of carbonaceous matter covers the primary silica cement layers. The central spaces between grains not occupied by the silica layers and carbon films, is filled with chert.

From this we can say that the well-rounded, large quatrz and pyrite grains suggest the sandstone was deposited in a high energy environment, such as a beach or estuary. The sandstone is also very clean - there is no fine material such as silt or clay - also supporting a high energy environment of deposition which would have washed out all the fine-grained material such as silt and clay.

The several episodes of silica cementation suggests cyclic inundation of silica-rich fluids into porous, clean sands.

Thin section showing b, Rounded quartz grain separated from a carbon-rich chert infilling by a dripstone cement (white arrow). c, Rounded grain of detrital pyrite (black grain) with a dripstone chert cement and carbon coating (red arrow). (Wacey et al. 2011).

The dripstone cements are exactly that, they appear as 'drips' of cement on the bottom on grains. This is because they form when the grains are exposed to air and trapped fluid flows to the bottom of the grains. This supports a beach-type environment which was influenced by valdose conditions - where non-marine groundwater is retained by adhesion to grains or by capillary action.

The evidence suggests then, that the sandstone was deposited in a nearshore beach-type environment which helped smooth out the quatrz and pyrite grains, and removed any fine material. During this time the first layer of carbonaceous material was formed around the grains (C1 above). Periodically, the highly porous sand came under the influence of valdose conditions, allowing the precipitation of silica cement around the grains (S1 above), trapping the carbonaceous layer, but maintaining the porous nature of the sand. Subsequently a second layer of carbonaceous material (C2 above) was formed over the S1 cement, possibly suggestive of a reversion to marine influences. A second round of valdose conditions produced a second cementation layer (S2 above). Followed by another return to marine influences and a third carbonaceous layer (C3 above). Finally, after the sands were buried, subsequent chert deposition provided the source for the last event, the filling of the remaining pore space with chert.

Before we look at the carbonaceous material in more detail there is the question of the link between the detrital pyrite grains and the carbonaceous matter.

The detrital pyrite grains are large, much larger than the possible cells in the carbonaceous matter, and are rounded. This suggests that the pyrite is not a product of possible organic activity. There is some pyrite within the carbonaceous matter, but this pyrite is much smaller and angular in shape - as expected if they have been precipitated as a result of organic activity. The detrital pyrite grains are also covered by the silica cement layers. The evidence suggests that the pyrite is primary - that is it was present as an original constituent of the sand - rather then being a product of organic activity. As the pyrite only occurs in the base of the sandstone, primarily in erosive channels in the underlying volcanics, it seems likely that the pyrite grains were formed from the erosion of underlying rocks and have been left behind as a lag deposit as pyrite grains are much heavier that similar sized grains formed from other materials like quartz. The renewed influx of sediment resulted in the pyrite grains mixing with the quartz grains to form a pyrite-rich basal sand. Subsequent deposts of sand did not have the pyrite grains and so were deposited free of pyrite and carbonaceous matter. Remember also that the 3.4 Bya atmosphere has precious little in the way of free oxygen, so the pyrite would be quite stable under surface conditions.

Since the detrital pyrite and carbonaceous matter are absent from the sandstone above the basal layer, there does appear to be a connection between the detrital pyrite and the carbonaceous matter. It appears that the carbonaceous matter is present because of the pyrite.

To answer why the carbonaceous matter should be linked to the pyrite, we first need to know what the carbonaceous matter is and what it contains.

Wacey et al. have found a number of elements (at right) in the carbonaceous film that look like prokaryote cells (or at least what prokaryote cells would look like after 3.4 billion years). So the question is, are we dealing with 3.4 billion year old microfossils?

Ramen spectroscopy (it's to do with lasers and nothing to do with Arthur C. Clarke) supports a disordered structure. This is important because organic matter is disordered, inorganic carbonaceous matter is ordered - abiotic graphite, for example, is found in rocks of this age but shows a well ordered internal structure. So that's a tick for organic. Also, an analysis of the structures indicates the presence of carbon, nitrogen and sulphur in the possible cell wall structures. Again a tick for organic as these are essential for organically formed structures, but not for inorganic ones.. Finally analysis of the carbon in the possible cell walls shows a 26-39 parts per thousand enrichment in ¹²C compared with atmospheric CO2. This also support the structures being organic as only organic activity can partition light ¹²C from the 'heavier' ¹³C to such an extent.

So the evidence suggests that the structures are organic, but are they microfossils?

Well, the shapes are round and tube-shaped. So, as prokaryotes tend to be round and tube-shaped, this is a good thing. However, a number of inorganic processes can produce round and tube shapes. So, by itself, this doesn’t tell us much. The specimens do show some evidence of folding, which organic shapes would do that inorganically produced shapes wouldn’t. So shape is a point in favour of them being microfossils, but not conclusive.

Size is an interesting one. Prokaryotes come in a range of sizes, but modern forms are generally around the 10 μm mark. The forms found range in size from 5-25 μm, with an average size of around 10 μm, not a bad comparison with modern forms.

Size distributions of microfossils from the Strelley Pool Sandstone compared to those from three younger biological microfossil assemblages and one abiotic spherulite assemblage. (Wacey et al. 2011).

Also the distribution of sizes is similar to that of other accepted fossil forms in the 1.9 billion year old Gunflint Chert of Ontario and the 0.8 billion year old Bitter Springs formation of Central Australia. These latter fossils are considered to be Prokaryote fossils. However, this does not represent the total distribution.

80 μm giant from Wacey et al. 2011

As Wacey et al. state, and PZ has discussed, there are larger specimens, if rare, up to 80 μm in size (see left), which is much larger that normal. However, prokaryotes do exhibit larger size ranges, so it is not implausible that cells could range up to this size.

Another explanation could be that these large ‘cells’ represent a cluster of cells in which only the outer cell walls in contact with pore fluids have been preserved, while the internal walls dividing individual cells are not preserved. Certainly the structures arrowd in the large specimen could represent the boundaries between cells as much as they could represent folding. The presence of silica micro-crystals in cell walls does suggest that silica-rich pore fluids played a part in the preservation process. So the larger specimens could be the remains of clumps of cells, or possibly a different group of organisms from the smaller ones.

The numerous lines of evidence tends to support the identification of these structures as organic ans potentially prokaryote cells, making them the oldest life forms so far identified.

So why the attraction to sulphur? Well, in the absence of oxygen, SO₄^2- makes a good terminal electron acceptor. Larry Moran has the details.

Given the age, it will probably be impossible to get absolute evidence that any particular set of structures represent Archaen prokaryotes, but the evidence Wacey et al. 2011 present is probably as close as we could reasonably expect to come.

So with these Archaen prokaryotes, and the Ediacaran fauna, when it comes to Precambrian life, AUSTRALIA ROCKS!

Wacey, D., Kilburn1, M.R., Saunders, M., Cliff, J. and Brasier, M.D (2011) Microfossils of sulphur-metabolizing cells in 3.4-billion-year-old rocks of Western Australia. Nature Geoscience. Published online Aug. 21. DOI: 10.1038/NGEO1238

Palaeoporn 23

2011-08-13T17:04:00.000+10:00

Indiana Nedin and the Temple of Kaili

OK, I'm back, after several months of work and travel, which included losing the top of the Eiffel Tower, and finding it again, avoiding an ~~Ebola~~ E-coli outbreak in Hamburg, and retracing the route of The Italian Job in Torino, it's about time I got back to some real work and started posting on the blog again!

Continuing the tradition of famous fossil sites wot I have visited, the photo above (taken a few years ago now) is of me doing my Indiana Jones impression on a hilltop at the site of the Kaili Formation in Guizhou province, southwest China, some 550 kilometres ENE of Kunming and the Changjiang fauna.

The Kaili formation is basal Middle Cambrian in age (see figure at right) and contains the Kaili Biota, a Changjiang/Burgess Shale type lagerstätte. Given it's age, the biota sits midway in age between the Lower Cambrian Changjiang fauna and the Middle Cambrian Burgess Shale fauna.

As would be expected, the Kaili biota shows significant overlap with both the Chengjiang and Burgess faunas in terms on genera in common. Wikipedia, suggests that of the (quite diverse) 110 genera occurring in the Kaili biota, 30 are shared with the Chengjiang fauna, and 40 are shared with the Burgess fauna.

The Kaili biota is thought to represent an outer-shelf environment and contains large numbers of planktonic trilobites, and eocrinoids, along with a range of soft bodied forms such as neroiids, Wiwaxia and Marrella

However, that's not what I want to talk about. See the village to my right in the photo above (click on the photo to enlarge)? That was our way down from the site. That's what I want to talk about because when we entered the village we were greeted with this:

We had entered a village of the Mountain Miao Minority Peoples of Guizhou, and they laid on a traditional welcome ceremony for us. This started with two local girls in full traditional costume offering food and drink to each person as they entered. The traditional dress included amazing jewelry in solid silver! On this occasion we were offered fish and some lethal alcoholic local brew from a ceremonial horn.

Once inside we were treated to a series of traditional dances, again performed by the girls of the village complete with elaborate gorgeous silver jewelry.

We were not informed that this was going to happen so it was a complete surprise. It was an amazing experience, and was the perfect end to the day.

Further Reading

ZHAO Yuanlong, ZHU Maoyan, Loren E. BABCOCK, YUAN Jinliang, Ronald L. PARSLEY, PENG Jin1, YANG Xinglian1, WANG Yue1 (2005) Kaili Biota: A Taphonomic Window on Diversification of Metazoans from the Basal Middle Cambrian: Guizhou, China. Acta Geologica Sinica; 79(6) 751–765. DOI: 10.1111/j.1755-6724.2005.tb00928.x

Paris June 2011

2011-07-16T14:54:00.000+10:00

Good news. The bit of the Eiffel Tower that was missing in February is now back.

Hamburg

2011-05-20T21:34:00.000+10:00

Things have been a bit quiet recently because inexplicably, the people who pay me actually want me to do stuff!

Part of that stuff will have me at a loose end in Hamburg on the weekend of 11th and 12th June. So if anyone has any suggestions about things to do in Hamburg, I'd be grateful for some tips.

Meanwhile, normal service will be resumed as soon as possible

Mopping up some Ediacaran Enigmatics

2011-04-03T15:36:00.000+10:00

The most common form of preservation of Ediacaran fossils in the Flinders Ranges of South Australia is by sands covering objects on the sea floor and masking them. Much of the sea floor was covered with algal and bacterial mats, or films, that add an extra dimension to the structures preserved by the covering sands. We have to take this extra dimension into account if we are to successfully interpret what it is that has been preserved. Some organisms lived on the mats, some below, and some had elements below and elements above. Understanding the interactions between organism, mat and sand will allow us to better understand what was going on at the time and help separate out body fossils from trace fossils from non-biogenic traces.

A good example of this are "mops".

"Mops" are a series of abundant, distinct structures which look like the head of a mop - hence the name. "Mops" are always preserved in hyporelief, that is on the underside of the rock, unusually though, they can be either positive - standing up from the surface like a pimple, or negative - a depression in the surface like a dimple. Most Ediacaran fossils are usually either one or the other.

Tarhen et al. studied a series of "mops" which show a highly varied shape and structure, but found some consistent features.

Mop structures in hyporelief from the Ediacaran of South Australia.
Scale bar = 2cm. (Tarhan et al. 2010)

(1) "Mops" are always orientated within 10 degrees of the palaeocurrent as derived from a number lines of evidence.

(2) They have a distinct margin at one end - considered to be the distal or far end. This can be straight (arrowed in (A) above), curved (in (B)) or lumpy (in (C)).

(3) They have a series of roughly parallel lines running at around 90 degrees to the margin (arrowed in (B) above). These appear filament-like and can be either linear or wavy and tangled

These features can vary even within the same bed and between specimens in close proximity.

They do tend to appear in close association with the disc form Aspidella, which it though to represent the holdfast of a Charniodiscus-like organism or sea pen. But are they fossils or non-biogenic marks?

Well they appear biogenic. The association with Aspidella is too strong to be random. But are they body or trace fossil? Well, they are a little of both.

The association with Aspidella appears important. Aspidella is the holdfast of a sea pen-like organism, which had a large bulbous holdfast buried in the sediment, with a stalk and frond rising up into the water column. So the organism has some elements (the holdfast) below the bacterial mat, and some (the frond) above the mat.

In this configuration, the frond will be subject to water currents. What is though to have happened is that strong currents carrying the sand that will eventually overlay the organisms has hit the frond and basically dragged the whole organism including the holdfast, in the direction of the palaeocurrent. As the holdfast is under the mats, this dragging has uprooted the holdfast and dragged it through the microbially bound mat layer. The parallel lines represent torn-up bits of mat which were attached to the top of the holdfast. Lumpy margins of the 'mops' are probably caused by small lumps of sediment trapped next to the holdfast.

Formation of "mops". A: Normal conditions. B: Current drag. C: Current induced structures.
D: Sand deposition. E: Preservation. (Tarhan et al. 2010)

This explanation can explain a number of structures seen in Ediacaran rocks. One in particular is Pseudorhizostomites.

Pseudorhizostomites. Scale bar = 2 cm. (Tarhan et al. 2010).

Pseudorhizostomites has been interpreted as a rhizostomean medusa (a jellyfish without tentacles), and even a gas escape structure formed during the decay of an organism. But an interesting interpretation based on the 'mop' formation, is that they are Aspidella-like holdfasts that have been torn free by current action, but vertically rather than in a more horizontal direction. So they have been plucked out of the sediment rather than being dragged along.

Another structure that appears related is one associated with actual holdfasts.

Here the holdfast has remained intact and in place, but the stem has been flattened and the surface of the holdfast has been distorted by the sheer forces caused by the current pushing the frond and stem over.

Here is an annotated example that has been featured here before. The wrinkles (W) and the impression of the stem (S) are clearly visible and have been caused by the stem and frond being pushed over by a strong current which eventually deposited the overlying sand bed

The explanation of the "mop" structures is a neat use of the interplay between sedimentology and taphonomy, that ties together a number of structures.

Tarhan, L.G., Droser, M.L. and Gelhing, J.G (2010) Taphonomic Controls on Ediacaran Diversity: Uncovering the Holdfast Origin of Morphologically Variable Enigmatic Structures. Palaios V. 25, pp 823-830. DOI:10.2110/palo.2010.p10-074r

New Find Challenges Evolution

2011-04-01T00:11:00.000+11:00

I've been a passionate supporter of evolution, but now . . .

A recent find from the Flinders Ranges of South Australia will shake the theory of evolution to the core. But no-one knows about it.

Why?

I've tried to talk to palaeontologists about it, but the refuse to discuss it. Evolutionists I've known for years no longer reply to my emails. I've been ignored buy organising committees for conferences and symposiums in favour of other evolutionists when I have earth shattering evidence against their pet theory.

They may have frozen me out, but I will not be silenced.

From a Precambrian site deep in the Flinders Ranges, I was guides by something . . . or someone, and I found startling remains - reptile remains with clear preservation of skin. How could that be if the 'so called' (in my opinion now) theory of evolution is true? How can exceptionally preserved reptile remains be present at a Precambrian site?

It can't. But it is. So evolution must be false.

Click on the link below and spread the evidence the the evolutionists have tried to stop me from exposing.

Reptiles in the Precambrian disproves evolution

Paris Feb 2011

2011-02-17T13:59:00.000+11:00

Something told me I'd picked the wrong day to check out the view from the top of the Eiffel Tower . . .

Palaeoporn 22

2011-02-02T21:13:00.005+11:00

Treptichnus pedum

The type section for the Cambrian-Precambrian boundary is at Fortune Head, Burin Peninsula, Newfoundland, as is marked by the first appearance of the trace fossil Treptichnus pedum (the trace fossil formally known as Phycoides pedum).

Treptichnus pedum is a distinctive burrow pattern comprised of a series of lobes set along a central, sometimes curved burrow, thought to represent successive probes into the sediment searching for food. The traces are thought to represent an organism more complex that those of the Ediacaran, but that is not necessarily true, as no actual animal has been found is association with the burrows, so we don't know what made them (although modern priapulid worms make similar burrows).

However, we should not confuse the somewhat complicated pattern of Treptichnus pedum with the first occurrence of well-developed, fairly complex metazoan animals.

While the start of the Cambrian is marked by the first appearance of Treptichnus pedum, this is not the first appearance of trace fossils probably from metazoans. A number of trace fossil types exist in the preceding Ediacaran rocks. In fact they show a neat line in increasing complexity from simple traces early in the Ediacaran to traces as complex as T. pedum towards the end of the Ediacaran.

The earliest traces we have, and the most simple, is Planolites

This is a lowermost Cambrian specimen (picture from NCSE), but it shows you what they are like. The fossil is of simple, cylindrical, unbranched and unlined burrows. They are usually sinuous and undulatory, and often appear as small knobs or discontinuous segments on bedding planes. The small image below is what they typically look like in Ediacaran rocks

Further up in the Ediacaran, more traces appear. This is Helminthopsis

Helminthopsis are much more meandering burrows that appear to represent shallow feeding burrows. the distinctive whorls and loops are considered to represent a different feeding strategy to that of Planolites.

Towards the top of the Ediacaran, things get a bit more complex. As well as Planolites and Helminthopsis, we get the feeding traces of Kimberella.

Here, the feeding traces are marked "R" for radula, and the animal itself is marked "K". A Dickinsonia is also present. "K'" and "D'" mark the resting trace of Kimberella and Dickinsonia, which comprise, of course, another form of trace fossil.

Towards the top of the Ediacaran, things start to get crowded. Not only do we have all the previous traces, but they are joined by Mattaia miettensis.

This specimen comes from the Kessyusa Formation, from Khorbusuonka in northern Siberia. The trace is filled with two bands of sediment, raised on the sides and depressed in the middle, where the bands are separated by a vertical fissure filled with clay. A possible culprit is a pripulid worm such as the Burgess Shale form Louisella pedunculata.

So by the time you get to the Cambrian-Precambrian boundary there were quite a few traces around. Sure in the Cambrian the traces get much more diverse, but they don't start at the boundary, there is a steady increase in trace fossils through the Ediacaran.

Update
Aleksey Nagovitsyn has kindly informed me that the age range for Mattaia miettensis in Palaoeporn 22 is incorrect, and Mattaia miettensis is actually to be found in the Cambrian Tommotian Stage of the Cambrian.

So we need to remove Mattaia miettensis from the list of trace fossils found at the top of the Ediacaran.

"You Cannot Trust Reasons to Believe"

2011-01-14T18:36:00.004+11:00

At least that's what Todd Wood thinks.

In a series of detailed posts, Todd does an excellent job of taking apart a series of posts and responses by Dr Fuzale Rana of Reasons to Believe (a christian group that "bridges the gap between science and faith by exploring questions about God and the Bible". They have no problem with an ancient Earth, but evolution is apparently another matter) on the similarity between the human and chimp genome (or not, in the case of Reasons to Believe) and moves on to pseudogenes, thus:

"In his latest post, Rana asserts the following about the argument for common ancestry from pseudogenes:

When evolutionary biologists present this argument, they make a number of assumptions, all of which appear to have questionable validity based on recent research results. For the pseudogene evidence to have potency: (1) pseudogenes must lack function; (2) their origin must be due to rare, random events; and (3) their juxtaposition to other genes must be arbitrary.

Everything he wrote there is utterly false. None of those conditions are required to argue for common ancestry from pseudogene similarity. Not one."

Ouch!

Well, you may say, 'showing up the mangling of science by those seeking to support their religious views, is not unusual".

True. But Todd happens to be a young earth creationist.

Double ouch!

Here is post one, from there move on to "Newer Post" and read them in sequence. Post four is at the bottom of the front page of Todd's blog. You can work your way up.

It's well worth the read.

Palaeoporn 21

2011-01-09T13:39:00.010+11:00

Beltanelliformis brunsae

In keeping with the positive hyporeliefian, is-it-or-isn't-it-a-metazoan theme of the last couple of posts, here is Beltanelliformis brunsae. A widespread form (this one is from the Mackenzie Mountains of Canada) that has had a history of being moved around the tree of life.

Notice firstly the texture of the surface. This is a microbial mat that has undergone some considerable deformation, probably due to the sudden influx of sand which pressed down on the mat and caused it react unevenly to the sudden load.

The Beltanelliformis appear at first glance to be similar to other disc-like Ediacaran forms associated with holdfasts. However, notice that the specimens pictures are in strong positive hyporelief, that is they extend quite some way out from the lower surface of the sandstone. This means that the sand infilled quite a sizable hole in the underlying mud. Notice also that, in the top two specimens, the fossil has a 'collar' around the basal disc, which makes the hole infilled by the sand cone-shaped, with the base being the smaller diameter part of the cone.

This configuration let to suggestions that the form represents the burrow of an anemone.

Below is a representation of that interpretation (from Schopf et al.).

However, more recent interpretations have Beltanelliformis as an algae.

What!? Algae!?

Yes, algae. Here's why.

The uppermost Doushantuo Formation (590-555 Ma) at Miaohe in the Yangtze Gorges area, is a series of dolomites that provide a rare Burgess-Shale-type taphonomic window on the Ediacaran. Within the Formation are found numerous carbonate compressions of organisms. This represents a different mode of preservation to that of the more typical sandstone preservation, at Miaho the forms are flattened carbonate compressions. Amongst the forms present are several that are interpreted as Beltanelliformis

Beltanelliformis brunsae from the Doushantuo Formation. Scale in 2, 1 cm. from Xiao et al. 2002)

The non-overlapping nature of the fossils is a good indication that we are dealing with benthic (bottom-dwelling) forms and not free-swimming forms that have died and sunk to the bottom. It may well be that the forms were actually tethered to bottom with a small holdfast structure.

The Doushantuo specimens have thing flexible walls. However, given the original specimen at the beginning of this post, it's clear that they would need to retain the three-dimensional shape during burial by sand.

A modern form that appears to fit the bill is the caulerpalean green alga Derbesia (photo credit).

Derbesia is benthic, is attached by a minute holdfast, and has the right shape and size. Also, it is organized as a coenocytic film of cytoplasm within a elastic and strong wall and surrounding one or more large, fluid-filled vacuoles. These vacuoles would be sealed and so couldn't empty on burial like holdfasts could. This makes it strong enough to make an impression in sandstone preservation!

So Beltanelliformis has gone from Cnidarian -> holdfast -> anemone burrow -> algae with holdfast.

Interestingly, apart from Nimbia and Aspidella mentioned in a previous post, Beltanelliformis has one of the longest time ranges, having been found in the pre-Ediacaran Cryogenian in Canada.

This again raised the possibility that several of the generic Ediacaran disc fossils could be something other than metazoans. That's actually fine. We have enough evidence that some of the discs represent metazoans. That some don't, should be expected. After all, if the Ediacaran assemblages represent vibrant, healthy ecosystems, they would be expected to contain microbial, algal, and metazoan, life.

To Epirelief or Hyporelief, That is the Question . . .

2011-01-03T23:37:00.011+11:00

My last post on the possible 770 million year old Ediacaran fossils from Kazakhstan prompted some comments regarding epi- and hyporelief (go read the post and comments).

Basically, Ediacaran fossils are usually found on the underside of the sandstone bed in either positive relief (sticking out from the surface) or negative (sunk into the surface) hyporelief (hypo- is sciencey for 'on the underside'). This is dictated by the mode of preservation (again see the original post), and means that we do not find them on the top surface of the sandstone bed, or in epirelief. (Actually we do find them in epirelief, but only at Mistaken Point in Newfoundland where they have been mantled by volcanic ash - but that appears to be a one off and so does not represent normal preservation).

As an example here is a slab I collected from the Flinders Ranges in South Australia. First the upper (epi) surface.

As you can see, its rippled - strongly rippled actually - which puts pay to the ideas that the Ediacaran faunas were deep water, but that's another story. However, what the top surface isn't, is fossiliferous. There are no fossils on it.

Now lets take a look at what's underneath.

Ta Da! This was taken in situ, about 5 minutes after I'd found it. The photo is a bit blurry 'cos my hands were stili shaking!

Notice the smooth lower surface. This is because it is mantling a mud which does not form ripples. Also notice that there are three large discs in positive hyporelief and a Dickinsonia in negative hyporelief. What do you mean no!?. Ok, here's an annotated version.

The question has been asked why the counterpart of a positive hyporelief isn't a negative epirelief on the bed below. In other words if the fossil is formed by sand flowing into a depression in the underlying mud to form a positive hyporelief, should there also be a corresponding negative epirelief on the top of the underlying bed?

The answer is yes, but we almost never find them. The reason is that the underlying bed is made of mud and so compresses during diagenesis which disrupts the fossil. However, the main reason is that the mudstone weathers much more readily than the sandstone and forms a very friable, crumbly rock that simply weathers away.

We do have some examples of underlying epirelief fossils, but they are very rare. To find them you have to excavate the sandstone with the underlying mudstone still in place. Even then, they are very fragile. Normally this never happens in nature as the mudstone erodes away. The fossiliferous sandstone then weathers out and falls downslope to be found by palaeontologists.

Below is a typical Ediacaran location. The fossils are eroding off the top of the hill and can just be seen in outcrop. but the fossils are found on the scree slope, as float - that is, material that has eroded out of the outcrop and has slid downslope

So the answer is, yes there are there epirelief fossils but we almost never find them as they have weathered away. But they would be in mudstones and not in sandstones.

770Ma Ediacara (?) Fossils from Kazakhstan (sadly no)

2011-01-02T16:53:00.000+11:00

The Ediacaran Period represents that youngest part of the Proterozoic, and is famous for the first appearance of multicellular, metazoan fossils. The Period starts at the end of the great neoProterozoic Cryogenian, or glaciations - commonly called "Snowball Earth" - at around 635 million years ago, and ends at the start of the Cambrian (and Phanerozoic) at around 542 million yeras ago. While a few Ediacaran stragglers may appear in the Lower Cambrian, no unambiguous multicellular/metazoan fossils have been found below the base of the Ediacaran Period, despite several possible candidates (e.g here and here).

In a new paper, Meert et al. report the possible occurrence of Ediacaran fossils from 760-770 million year old Cryogenian rocks of Kazakhstan. If correct, this would extend the fossil record of metazoans back another 100 million years. Now, there is some evidence to suggest that metazoans were around in the Cryogenian, if only at the sponge-grade of organisation, but this is from biochemistry, not body fossils. So this would be the oldest metazoan body fossils yet found.

Two questions to be asked then. Are these deposits c. 770 million years old? Are these specimens examples of Ediacaran fossils?

I think the answer to the first question is yes, and the answer to the second question is no. I'll explain below.

Age
I have to say that Meert et al. have done an excellent job of mapping and correlating what appears to be a very difficult sequence. It's condensed and so quite thin (by contrast, the Ediacaran type section in Australia is several kilometres thick), a significant portion missing, and the area has been subsequently affected by tectonics.

Stratigraphic column for the Lesser Karatau sequence showing the relative locations of the fossil discoveries. The fossils under discussion are from the Upper Riphean Kurgan Formation (R3) (in brown) and the glacial deposits (in yellow) and cap carbonate represents the end of the Cryogenian glacial episode and the start of the Ediacaran Period. (Meert et al. 2010)

Now with a section like this it could be argued that the glacial rocks and cap carbonate represent glacial activity known to occur in the Ediacaran and that the underlying rocks are, in fact, Ediacaran. But I think Meert et al. have compiled enough evidence to support their stratigraphy. This includes radiometic dating of two separate samples from the Kurgan Formation that support a c. 770 million year age, as well as a δ13C stable isotopic curve that fits their interpretation (given the fragmentary nature of the curve, it could fit a number of scenarios, but it does fit this one.)

So notwithstanding the difficulties of the section, the date appears well supported. We appear to be dealing with c. 770 million year old rocks.

Fossils
1) Disc and stalk
Meert et al. have found structures in the c. 770 million year old Kergan Formation which they suggest may be referable to the Ediacaran forms Nimbia and Aspidella, as well as a second line of evidence, a possible stem extension emanating from the discoid fossil, and ask the question, are these Ediacaran fossils? As I said, I think the answer is no.

To show why, firstly I need to explain a bit about Ediacaran fossil preservation and positive/negative epi/hyporelief.

Ediacaran fossils occur primarily as marking on the surface of sandstones. These surface markings can be of two types, positive - standing up from the surface like a pimple, or negative - a depression in the surface like a dimple. Also the sandstone has two surfaces, a top surface - the epi-, and a lower surface - the hypo. Thus when we talk about surface structure, or "relief" - we talk of structure on the top bedding surface - epirelief, and structure on the lower bedding surface - hyporelief. So positive epirelief is a raised area on the top surface and negative hyporelief is a depression in the lower surface.

This is important because Ediacaran fossils occur as positive or negative relief on the bedding surfaces, but almost always as positive or negative hyporelief - that is, on the bottom surface.

The reason for this is that preservation is by sand covering a surface that has animals on it. The sand (which will eventually turn into sandstone) covers the animals. Where the animal is tough, it will push into the overlying sand, causing a negative hyporelief impression (of the top surface of the animal) into the bottom surface of the sand. Where the animal is buried in the underlying sediment, such as holdfasts, the sand flows into the depression caused by the collapse of the holdfast during burial, causing a positive hyporelief impression.

The example above is of the lower surface, The Form D projects out from the surface and so is a positive hyporelief impression (the overlying sand has pushed down into the Form D stolon structure to form the impression. By contrast, the Parvancorina has pushed up into the overlying sand and so is preserved as a negative hyporelief impression.

OK, lets deal with the second line of evidence first - the possible stem extension emanating from a possible discoid fossil.

(A) Discoidal impression (negative relief) with possible stem-like extension. (B) Sketch showing the location of discoidal fossil and possible stem. Meert et al. 2010.

Just to be clear about what is being discussed, here (at left) is a modern sea pen (photo credit) we can use as an example of the frondose forms around in the Ediacaran. The structure half-buried in the sediment is the disc-shaped holdfast. Underneath the holdfast is a thin tube - the peduncle - which acts like the foot of a clam and aids in digging the organism into the sediment. The stem and frond extend out into the water column and the whole thing is held up by water pressure. The organism can inflate by pumping water into the holdfast to allow it to act as an anchor, and also into the stem and frond to hold them rigid. Pumping water out deflates the organism. Modern sea pens will deflate on touching, and collapse down onto the sediment, as a method to avoid predation or damage.

According to Meert et al., their find may represent a holdfast and part of the attached stem that has made an impression in the sediment, in negative relief. The authors do not say if the surface is the top or bottom (and they may not know if the sample was collected loose and not found in situ.

However, holdfast impressions are almost always found as positive hyporelief impressions, i.e. they stick out from the lower surface. They are not found as negative relief, i.e. as depressions, as the Kurgan Formation specimen is. To find out why that is, let's look at an example.

Three-dimensional positive hyporelief fossil of a holdfast and stem from the Ediacaran of South Australia. HF impression of holdfast, IS intermediary surface within the sandstone, LS lower surface of sandstone, P peduncle, S impression of stem, W wrinkles in top surface of holdfast. White arrow is the direction of current depositing the sand.

Above is an actual Ediacaran holdfast and stem fossil. There's a lot going on here (compared with the Meert et al. specimen where no structure is present) so it'll take a bit of explaining.

Firstly observe that this is in positive hyporelief - it's on the bottom surface of the bed. As I said, pretty much all holdfast fossils with stems are positive hyporelief. This is because the organism is sitting in the underlying sediment and gets inundated and covered by a mantling sand deposit which will become the overlying sandstone bed. Since frondose forms will deflate on contact with the enveloping sandstone, the organism pumps out water and collapses. This means that the stem falls over, usually in the direction of sand transport. The stem often gets trapped within the sand and rarely comes to rest on the sea floor because the sand has started to deposit as the organism responds. This normally results in the stem coming to rest at an shallow angle to the sea floor/base of the sand body - that is, it sticks up at an angle into the sand rather than laying down flat. This can be seen in the Ediacaran example shown above. The stem impression (S) can be seen heading off at the ten o'clock direction but it is obviously heading off into the sandstone - the edge of the stem impression is lower in the sandstone than the impression of the holdfast, and, as this specimen is shown upside down, the stem in heading upwards into the overlying sandstone.

The wrinkling texture is the upper surface of the holdfast reacting to the stem being pushed over and collapsing and shows that the holdfast stayed in place during burial.

The organism is now covered by a layer of sand, with the stem trapped within the sand at a shallow angle. As the water has been pumped out, the holdfast will no longer stay inflated and so the holdfast upper surface sinks down onto the lower surface causing a shallow depression. The upper surface also takes on the shape of the lower surface where the hollow peduncle is, creating a ring shape (P). The overlying sand then flows into the shallow depression and takes on the shape of the combined lower and upper holdfast surface structures in a process called gravity casting. Also, as the stem is angled upwards, the sand with collect behind it and be trapped between the stem and the holdfast. We can see this is the example above. The sandstone covering the stem has been removed, leaving a lighter coloured sandstone. The stem starts out on top of the holdfast, but ends up on a lower, intermediate surface (IS) (lower from our prespective, higher when the specimen is rotated to the correct orientation).

What you end up with is a positive hyporelief impression of the combined upper and lower holdfast surface, plus the base of the stem. Furthermore, this is the only way this can be preserved. We tend not to see holdfast impressions on the tops of sandstones because the organisms appeared to favour softer, finer sediments such as silts and clays, and where active microbial mats occur.

With that in mind lets look at the Meert et al. specimen again.

This time I've annotated it to mark out the various levels in the specimen, with A the highest, B an intermediary level, and C the lowest (assuming we are looking at the top surface, or the reverse if we are looking at the lower surface).

First of all, this is a negative relief. As I explained above, holdfast and stem preservation is usually by gravity casting which produces positive relief. If we are looking at a bottom surface, maybe the organism remained intact and 'pumped up', forming a hollow in the overlying sand. But in that case the stem would also remain intact and we wouldn't see the impression of the stem in the resultant fossil. So if the stem is represented, then the organism had collapsed, in which case the holdfast would have collapsed and we would get a positive hyporelief as notmal.

The structure can't be a positive hyporelief that has eroded out the produce the depression because the original fossil is just a surface impression. The sandstone underneath the fossil is the same sandstone the rest of the rock and so there can be no preferential weathering to produce the hollow.

If we are looking at a top surface, then it is unlikely to be a holdfast and stem as we do not find them on top surfaces of sandstones. Even if it were, the stem appears to have been pushed into the sand body to a level equal to, or even greater than, the depth of the holdfast. Again an unlikely occurrence, as a slight impression on the underlying sand is the most you are likely to get.

Given that this is a negative relief and the lack of any distinguishing structure, it is most likely that the specimen is simply an erosional feature and not a fossil.

2)Nimbia and Aspidella
Specimens referable to Nimbia and Aspidella are reported from the c. 770 millio year old Kurgan Formation.

Our specimens were discovered in a brown-red shale within the largely siliclastic Kurgan Formation and are preserved in both hypo and epi-relief. They are circular to oval-shaped impressions that surround either a smooth interior or circular to oval indentations with a smooth interior. (Meert et al. 2010.)

(A) closeup of the Nimbia fossils in positive epirelief, AT marks the occurrence of a possible invaginate morph of Aspidella terranovica; (B) B&W photo of Nimbia impressions shown mostly in positive epirelief; (C) Nimbia fossils in negative relief with a possible invaginate morph of Aspidella terranovica in positive relief; (D) large c. 2 cm (long axis) c. 1.5 cm (short axis) negative hyporelief impression of Nimbia occlusa and an ‘inversion’ of the photo the fossil might appear in positive epirelief. White arrow points to a possible raised central nodule observed in Nimbia occlusa fossils elsewhere. Meert et al. 2010.

Taking Aspidella first. Actually, attributing the form to Aspidella doesn't tell us much. This is because Aspidella should now be considered a form genus - that is a grouping of similar forms (i.e. discs) and not representative of a single organism, or related group of organisms. In other words, a lot of different things make disc impressions, e.g. algae (algal biscuits), microbial colonies, fungae and metazoans. Calling the specimen Aspidella simply says that it is a certain kind of disc, not that it is the Ediacaran form Aspidella terranovica. There are a lot of morphologies within the Aspidella group and they are not produced by the same organism, or even closely related organisms. This means that more than one organism is included under Aspidella. Even worse, no consistent distinction can be made between the various disk structures, making it difficult to accurately assign a particular disc to a particular organism. Where other evidence exists, i.e. stem impressions, ornamentation, etc, it is possible to identify individual organisms or groups of organisms. But simple discs remain probematic. Being a disc does not make it a holdfast!

It is entirely likely that Aspidella actually represents a group of diverse, not closely related, organisms - microbial, algal, fungal and metazoan - that produce discs and overlap each other to give Aspidella a large time range, but this time range is not for a single species or even genus.

This boils down to the fact that Aspidella with stems or other ornamentation, and associated with other Ediacaran forms, can be considered a metazoan fossil. Other Aspidella with no other ornamentation, and not associated with Ediacaran forms, could be anything.

The Nimbia find is in a similar situation. Do we have Nimbia? Yes. But here also, I think that the form Nimbia, like Aspidella, may hide a multitude of sins, or at the very least a number of different organisms. Except I think we have proof here that Nimbia is not an Ediacaran metazoan - or at least this Nimbia is not an Ediacaran metazoan.

The specimens of Nimbia from the Kurgan Formation are found as positive epirelief, negative epirelief, and negative hyporelief. This does not happen for Ediacaran fossils, as discussed above. Since these Nimbia show a number of modes of preservation, and they all show the same structure regardless of mode of preservation, it is apparent that the form that produced it is rigid. It has to be if it produced the same shape whether on the top surface creating a positive or negative imprints, or on the bottom surface. The fossil is the same independent of preservational style, and so whatever is causing the fossil must therefore be rigid like a coin. That rigidity, and the various preservational styles, means that it cannot be a holdfast.

It has been suggested that Nimbia represents microbial colonies. Hard, well agglutinated disk-shaped colonies would be tough enough to cause the impressions, and some have been known to develop a central nodule similar to that found in some Nimbia. This would explain the similar shape through different modes of preservation, and the large time range of the form.

Finally, Ediacaran fossils are normally found as assemblages, with a number of different forms present. The Kurgan Formation specimens are of one main type, Nimbia, and a few Aspidella. Too restricted to be considered an assemblage (a random collection would be expected to uncover more than two forms if an assemblage was present). Even if this find represented an early stage in the evolution of metazoa, it would be expected that more than two forms would be present.

So, discoial fossil with stem? - no. Aspidella? - yes, possibly, but that doesn't mean it's an Ediacaran or even metazoan. Nimbia? - yes, but probably not metazoan.

In properly posing questions about their finds instead of making pronouncements, and suggesting a number of possible interpretations for their finds, Meert at al. have highlighted the important implication of their finds.

It is possible that our discovery of Nimbia occlusa and Aspidella terranovica(?) in sedimentary rocks during the early Cryogenian (N766 Ma) lends support the alternative hypotheses regarding these fossils and remove them from consideration as true metazoa(Meert et al. 2010.)

I think they are right, they have provided evidence that the forms are not metazoan - or at least not "Ediacaran" (as in found amongst Ediacaran assemblages) - fossils, and that the simple disc-shaped forms found in the Proterozoic comprise a form group with contributions from a number of metazoan and non-metazoan sources.

Meert, J., Gibsher, A., Levashova, N., Grice, W., Kamenov, G., & Ryabinin, A. (2010). Glaciation and ~770Ma Ediacara (?) Fossils from the Lesser Karatau Microcontinent, Kazakhstan Gondwana Research DOI: 10.1016/j.gr.2010.11.008

Further reading on Ediacaran discs

Gehling, J.G., Narbonne, G.M., and Anderson, M.M (2000) The first named ediacaran body fossil Aspidella terranovica. Palaeontology, 43: 427-456. DOI: 10.1111/j.0031-0239.2000.00134.x

MacGabhann, B.A. (2007) Discoidal fossils of the Ediacaran biota: a review of current understanding. Geological Society, London, Special Publication, 286: 297-313. DOI: 10.1144/SP286.21

The Palaeontological Twelve Days of Christmas - Day 12

2010-12-29T12:01:00.000+11:00

Following on from the Twelve Geology Days of Christmas, this year we have a palaeontological version.

On the twelfth day of Christmas my true love sent to me, twelve insects in Australian amber entombing,
eleven ediacaran organisms evolving,
ten tiny T. rex tyrranizing,
nine Nigersaurus nibbling,
eight evolutionary digits encroaching,
seven seismosaurus stomping,
six snakes aslithering,

fiiiiive fossilllll fishhhhhhh,

four fossil footprints following,
three Tribrachidium tripartiting
two trilobites tasting,

and a Cambrian Lagerstätte.

The Palaeontological Twelve Days of Christmas - Day 11

2010-12-28T12:01:00.000+11:00

Following on from the Twelve Geology Days of Christmas, this year we have a palaeontological version.

On the eleventh day of Christmas my true love sent to me, eleven ediacaran organisms evolving,
ten tiny T. rex tyrranizing,
nine Nigersaurus nibbling,
eight evolutionary digits encroaching,
seven seismosaurus stomping,
six snakes aslithering,

fiiiiive fossilllll fishhhhhhh,

four fossil footprints following,
three Tribrachidium tripartiting
two trilobites tasting,

and a Cambrian Lagerstätte.

The Palaeontological Twelve days of Christmas - Day 10

2010-12-27T12:01:00.000+11:00

Following on from the Twelve Geology Days of Christmas, this year we have a palaeontological version.

On the tenth day of Christmas my true love sent to me, ten tiny T. rex tyrranizing,
nine Nigersaurus nibbling,
eight evolutionary digits encroaching,
seven seismosaurus stomping,
six snakes aslithering,

fiiiiive fossilllll fishhhhhhh,

four fossil footprints following,
three Tribrachidium tripartiting
two trilobites tasting,

and a Cambrian Lagerstätte.

The Palaeontological Twelve Days of Christmas - Day 9

2010-12-26T12:01:00.000+11:00

Following on from the Twelve Geology Days of Christmas, this year we have a palaeontological version.

On the ninth day of Christmas my true love sent to me, nine Nigersaurus nibbling,
eight evolutionary digits encroaching,
seven seismosaurus stomping,
six snakes aslithering,

fiiiiive fossilllll fishhhhhhh,

four fossil footprints following,
three Tribrachidium tripartiting
two trilobites tasting,

and a Cambrian Lagerstätte.

The Palaeontological Twelve Days of Christmas - Day 8

2010-12-25T12:01:00.000+11:00

Following on from the Twelve Geology Days of Christmas, this year we have a palaeontological version.

On the eighth day of Christmas my true love sent to me, eight evolutionary digits encroaching,
seven seismosaurus stomping,
six snakes aslithering,

fiiiiive fossilllll fishhhhhhh,

four fossil footprints following,
three Tribrachidium tripartiting
two trilobites tasting,

and a Cambrian Lagerstätte.

Why Dinosaurs Hate Christmas

2010-12-24T15:08:00.006+11:00

Back by popular demand, and new and improved (well it has a new diagram . . .)

Did you know that most dinosaurs hate Christmas? It’s true, they do. And it’s not because they couldn’t get a handle on the present wrapping (or unwrapping for that matter) either. No, there is a very good reason why Dinosaurs hate Christmas.

However, before explaining why dinosaurs hate Christmas, lets deal with some startling new information. Everyone is familiar with the standard explanation for the extinction of the dinosaurs. I've included a common representation of the event.

However, startling 'evidence' has been presented which suggests another reason for what happened. The evidence is still officially hidden by the authorities, but one startling image has been smuggled out and is shown here for the first time.

It is claimed that it was one of Santa's early experiments on propulsion systems that went wrong and had to be ejected. Shocking as this image is, there are some who claim that it is a forgery and just another shot by those at war with Christmas.

However, this is not the reason that dinosaurs hate Christmas. To understand that we need to know what dinosaurs are.

In his classic 1842 publication on dinosaurs, Richard Owen named and defined the Dinosauria as:
a group of exceedingly large, pachydermous reptiles from the Second Age . . . includes Megalosaurus, Iguanodon and Hylaeosaurus.

In 1997, Tom Holtz provided a different definition:
the last common ancestor of Megalosaurus andIguanodon and all its descendants. Using the same methodology, we can define dinosaurs as including the last common ancestor of the Herrerasauidae and the Hadrosauridae, and all their decendents.

Anyhow, the thing about this definition is that, nestled between the the Herrerasaurs and the Hadrosaurs, are the Dromaeosaurs, and directly related to the Dromaeosaurs, and so one of the descendants mentioned above, is a little group called Aves!

So with the mass slaughter of ~~birds~~ dinosaurs every Christmas, wouldn't you hate Christmas?

If you insist in participating in this slaughter, at least make sure you cook your dinosaur correctly:

1. If your dinosaur is frozen, fully thaw it.

2. Don’t stuff the dinosaur. By the time the stuffing reaches a safe temperature, the meat is overcooked.

3. Cover the dinosaur breast with ice while the rest of the dinosaur warms to room temperature. Don’t leave the dinosaur out for more than 3 hours. At this point, the breast will be about 4.5^oC (40^oF), while the rest of the meat will be at 15.5^oC (60^oF).

4. Put the dinosaur in the oven and cook according to your favorite recipe.

5. With a meat thermometer, check temperature. Take out of the oven when legs reach 82^oC(180^oF) and breast hits between 68-71^oC (155-160^oF).

Ho Ho Bleedin' Ho.

The Palaeontological Twelve Days of Christmas - Day 7

2010-12-24T12:01:00.000+11:00

Following on from the Twelve Geology Days of Christmas, this year we have a palaeontological version.

On the seventh day of Christmas my true love sent to me, seven seismosaurus stomping,
six snakes aslithering,

fiiiiive fossilllll fishhhhhhh,

four fossil footprints following,
three Tribrachidium tripartiting
two trilobites tasting,

and a Cambrian Lagerstätte.

The Palaeontological Twelve Days of Christmas - Day 6

2010-12-23T12:01:00.000+11:00

Following on from the Twelve Geology Days of Christmas, this year we have a palaeontological version.

On the sixth day of Christmas my true love sent to me, six snakes aslithering,

fiiiiive fossilllll fishhhhhhh,

four fossil footprints following,
three Tribrachidium tripartiting
two trilobites tasting,

and a Cambrian Lagerstätte.

The Palaeontological Twelve Days of Christmas - Day 5

2010-12-22T12:01:00.000+11:00

Following on from the Twelve Geology Days of Christmas, this year we have a palaeontological version.

On the fifth day of Christmas my true love sent to me,

fiiiiive fossilllll fishhhhhhh,

four fossil footprints following,
three Tribrachidium tripartiting
two trilobites tasting,

and a Cambrian Lagerstätte.

The Palaeontological Twelve Days of Christmas - Day 4

2010-12-21T12:01:00.001+11:00

Following on from the Twelve Geology Days of Christmas, this year we have a palaeontological version.

On the fourth day of Christmas my true love sent to me, four fossil footprints following,
three Tribrachidium tripartiting
two trilobites tasting,

and a Cambrian Lagerstätte.

The Palaeontological Twelve Days of Christmas - Day 3

2010-12-20T12:01:00.001+11:00

Following on from the Twelve Geology Days of Christmas, this year we have a palaeontological version.

On the third day of Christmas my true love sent to me, three Tribrachidium tripartiting,
two trilobites tasting,

and a Cambrian Lagerstätte.

The Palaeontological Twelve Days of Christmas - Day 2

2010-12-19T12:01:00.000+11:00

On the second day of Christmas my true love sent to me, two trilobites, and a Cambrian Lagerstätte.

The Palaeontological Twelve Days of Christmas - Day 1

2010-12-18T12:19:00.002+11:00

Following on from the Twelve Geology Days of Christmas, this year we have a palaeontological version.

On the first day of Christmas my true love sent to me, a Cambrian Lagerstätte.

Palaeoporn 20

2010-11-22T21:42:00.013+11:00

Pambikalbae hasenohrae

Frondose (frond-bearing) forms are the most complex and interesting of the Ediacaran fossils, but rare. This is because most of the organism lives above the sea floor, to which they are anchored by a round holdfast, and so are not preserved. A number of frondose forms have been found, but Pambikalbae is different.

Pambikalbae hasenohrae (a) complete block showing several specimens (upper right and lower left). Slab 45 cms. (b) same slab but tilted to show fossil is interlayers with the sandstone matrix (cracks on left side of slab). (c) part of the right hand frond in (a) showing a complex arrangement of chambers.

Pambikalbae was made up of numerous chambered vanes, making up a frond, supported by a tapering central stem and an anchoring stalk. Several series of chambers occured on the vanes, joined together at zigzag sutures, and were commonly filled with sediment on burial. However, the complexity is probably an artifact of complex composite moulding of various nearby chambers, one on the other. It appears that the chambers curve away from the central stem out to the free, or outer, margin. The chambers also appear to be set on the vane in a regular patter so as to limit overlap.

These chambers are big. Bigger than anything else so far found. Here's a reconstruction.

Pambikalbae is clearly not a pennatulacean or cnidarian 'sea pen' like Charnodiscus. However, it does contain characters that suggest an evolutionary grade of organisation comparable to known cnidarians. The configuration and size of the chambers seems ideal to house symbiotic algae or bacteria . . . however, here's some wild speculation.

There is a group of cnidarians which do share similarities with Pambikalbae, and that's the physophorid Siphonophorida. Here's one below (photo credit)

Interesting isn't it. The chambers are especially similar. However, there is one thing wrong. The physophorid is upside down. The chambers actually point downwards. Why? Because physophorids float, they are not anchored to the sea floor like Pambikalbae.

But it's not as problematic getting from Pambikalbae to a physophorid, as it would appear.

(a) inverted Pambikalbae. (b) a hypothtical ancestral 'calycophore' siphonophore. (c) generalised modern physonect.

Just change a water-filled bulb as an holdfast, for an air filled bulb for a float. Simple folding inwards of the holdfast could produce the physonect and ancestral calycophore pneumatophore. A futher point of comparison is that the vane of Pambikalbae has three serial rows of chambers, as in calycophore and physonect siphonophores.

So a frondose form with wanderlust as ancestral to the modern siphonophore cnidarians? Maybe. But is could also be a derived hyrozoan, or a sister group to the early Chondrophorina. Whatever it is, it ain't no pennatulacean!

Jenkins, R.J.F. and Nedin, C. (2007) The provenance and palaeobiology of a new multi-vane, chambered frodose organism from the ediacaran (later Neoproterozoic) of South Australia. In P. Vickers-Rich, P. and Komarower, P. (eds) The Rise and Fall of the Ediacaran Biota. Geological Society Special Publication 286, 195-222. doi: 10.1144/SP286.15

The Royal Society Archive and Optick Glaffes

2010-11-06T14:28:00.013+11:00

The Royal Society is 350 years old in 2010. To mark the event, the Royal Society archives have been made freely available online.

ALL of them.

From 1665.

350 years worth.

The archives contain more than 66,000 articles, including the first ever article published in the world's first science journal Philosophical Transactions.

Here's a nerdy quiz question for you to ask, "What was the subject of the first paper in the first scientific journal?" Answer - Optick Glaffes.

The archive will remain free to access until 30 November 2010. So go in now and download some original articles from people such as Mr Issac Newton (a promising young mathematiks Profeffor)

and a Mr Charles Darwin (recently back from an around-the-world cruise).

Lower Cambrian Sea Anemones from China

2010-11-05T15:12:00.006+11:00

Holotype and paratypes of Eolympia pediculata from Han et al. 2010

Yet more exquisitely preserved fossils from the phosphorite deposits in the lowest Cambrian sediments of the Kuanchuanpu Formation, Shaanxi, China. And by "lowest" they really mean lowest! The deposits are only a couple of million years younger that the Cambrian-PreCambrian boundary, which is currently taken as 542 million years ago.

The new fossils have been identified as a possible stem member of the Cnidarian Hexacorallia, suggesting that the diversification of the Cnidaria either occurred very rapidly after the start of the Cambrian, or, more likely (as far as I am concerned), in the Ediacaran.

I don't have much comment to make. The interpretation appears reasonable. The paper is freely available at PLoS (thank you PLoS). I would have liked some larger specimens, but the size is an artifact of the preservation.

There's a nice comparison with some extant polyps from an extant species.

Young polyps from a modern species, from Han et al. 2010

The similarity in form and size is striking. Morphological similarity isn't everything, but it's something!

The authors end with:

The cnidarian diversification might have occurred rather quickly during the early half of the Cambrian or it may be deeply rooted into the Neoproterozoic.

I prefer the latter option, which is a nice intro to Palaeoporn 20!

Han J, Kubota S, Uchida H-o, Stanley GD Jr, Yao X, et al. (2010) Tiny Sea Anemone from the Lower Cambrian of China. PLoS ONE 5(10): e13276. doi:10.1371/journal.pone.0013276

Palaeoporn 19

2010-10-11T22:04:00.007+11:00

Another holy grail

Ignore the cute baby buffalo. See that unprepossessing roadside quarry with the people sitting on a pile of rubble (click to enlarge)? Well that rubble is the type section for the Chengjiang fauna.

Yeah! Not so unprepossessing now, is it?!

The Chengjiang fauna occurs in the Maotianshan Shale, a member of the Lower Cambrian Chiungchussu formation. They are found about 5 km northwest of the Fuxian Lake, and 6 km northeast of Chengjiang, Yunnan, China.

The age of the fauna is between 525-520 million years old, significantly older than the Burgess Shale (at 505 million years ago), and the Emu Bay Shale (approx 515 million years old).

The Chengjiang fauna rivals that of the Burgess Shale in preservation and diversity. Although not in difficulty to get to. The Burgess Shale is a 3 hour hike. Here, you can drive right to the outcrop!

In this shot (click to enlarge) you can see the quarry from photo one in the middle distance. There is a bus parked next to it with some people in the road. The hill to the right is Maotian Mount (hence Maotianshan Shale)

In this photo (click to enlarge), I am right at the back in short sleeves and a broad-brimmed brown hat (I'm in the same position in the first photo). I'm there partly because it's in the shade, and partly because there were some nice fossils there (all went to Nanjing University for study).

The depositional environment was delta front prograding eastwards into an open sea. Most of the fossil layers appear to be episodic events onto the marine muds in front of the delta, possible storm induced deposition of clays and fine sand. There's not much evidence of transport, so most organisms were locals and were buried by a series of turbidity flows.

This is a smaller quarry close by (click to enlarge). The dark colour is the fresh colour of the Maotianshan Shale. It is black when fresh, but rapidly oxidises to a tan colour on exposure to air. This is near the top of the Maotianshan Shale. The pick axe handle in the middle of the shot is marking the topmost Maotianshan Shales. The very top of the handle is resting against the first influx of sands, which coarsen upward until they are topped by a large lenticular sandstone at the top of the sequence above my head. This represents the prograding delta as it moves out over the muds of the Maotianshan Shale - just like the sands of the Mississippi Delta are prograding out into the Gulf of Mexico.

Evolution Among the Trilobites - Part 2

2010-10-04T23:42:00.000+11:00

Meet the family. Estaingia (right) and Xystridura (left).
In Part 1 we looked at the growth patterns of the Early Cambrian trilobite Estaingia bilobata, using certain measurements from the head, or cranidium. In this part we'll compare and contrast those growth patterns with the Early Cambrian trilobite Xystridura templetonensis. You can click on any of the images and graphs to get a larger version.

The change through time in the appearance or rate of development of ancestral characters is known as Heterochrony, which comprises two basic phenomena (pay attention, there'll be a quiz at the end!):

Paedomorphosis - the retention of ancestral juvenile characteristics in a descendant adult. Paedomorphic forms usually pass through fewer morphological stages during growth than their ancestors (in other words less time as a juvenile you stop being a juvenile early, before you've shed all the baby characters). There are three types of peadomorphosis

Deceleration - the rate of morphological development is reduced during the juvenile phase (slower development, but the same amount of time is spent as a juvenile, so the same size as the ancestor, but you have not completed the juvenile development so have a baby-faced adult)
Hypomorphosis - the onset of maturity occurs at an earlier stage of development (same development but less time as a juvenile, so a smaller adult then the ancestor - still baby-faced though).
Post-displacement - a change in the timing of the onset of certain features, with one or more structures starting to develop at a later stage (the same amount of time is spent as a juvenile, so the same size as the ancestor, but the structures are smaller in the adult)

Peramorphosis - the appearance of ancestral adult features in the descendant juvenile stage (beards on a baby!). Here to there are three processes:

Acceleration - increasing the rate of morphological development (if maturity is also accelerated then adult will be smaller then the ancestral adult, if the onset of maturity is not affected, the the adult will be the same size as the ancestral adult).
Hypermorphosis - delayed maturity so the juvenile stage is extended (spend longer as a juvenile, so the adult is bigger)
Pre-displacement development of structures occurs at an earlier stage of development (same time as a juvenile, but structures more developed and bigger).

Before we look at a comparison between Estaingia and Xystridura, lets refresh what it is we are actually measuring (see Estaingiacranidium (or head) at right). The relevant measurements that we are interested in are; Cranidial Width (CW), which is literally the distance between the eyes; the Pre-glabella Field (PGF), which is the area in front of the large bulbous glabella (incidentally the pre-glabella field only runs to the shallow trench towards the front of the cranidium. In front of the trench is the doublure. That is folded underneath the cranidium in life, along the trench, and pops up during moulting); Glabella Length (GL), adding PGF and GL gives us a value for the length of the cranidium; Pre-Orbital Glabella (POG), which is the bit of the glabella that lies in front of a line drawn between the front tip of the eyes; and the distance between the end of the Axial (or Occipital) Furrow (the trench behind the glabella) and the back tip of the Eye Lobe (AF-EL). (Note that the figure is missing the free cheeks. This is because they are usually lost or repositioned during moulting. Trying to measure missing of displaced portion of the head would not allow accurate measurements. The measurements here, therefore, are all done on cranidia (without free cheeks).

The story is that Xystridura (Middle Cambrian) has evolved from Estaingia as represented by forms from the Emu Bay Shale (Lower Cambrian) through changes in the rate of development of certain characters, or hererochrony.

Now, to look at changes over time we will be comparing ratios, not individual characters. Individual characters will usually grow over time, but we are interested in how that character changes with growth. If the character increased with growth at a greater rate than other characters, then the ratio increases. If the character increases with growth at a lesser rate than other characters, then the ratio decreases. If the character increases at the same rate as other characters then there is no change in the ratio.

The first character we will look at is the distance between the back of the eye and the occipital furrow (AF-EL).

Measurements of meraspid Estaingia and Xystridura.
Xystridura measurements adapted from McNamara (1981).

Here, the ratio AF-EL/CL compared with cranidial length is plotted with growth (cranidial length is taken as a proxy for growth) for meraspid (juvenile) Estaingia (yellow) and Xystridura (black). Here the smallest (youngest) meraspids have the largest ratio, and as they grow that ratio decreases. This means that, with growth, the feature is increasing at a slower rate than the overall growth rate. We can also see that Estaingia and Xystridura plot together. This means that the juvenile growth pattern is the same for both. The big difference is that the Xystridura meraspids continue beyond the transition from Estaingia meraspid to holaspid (adult) (yellow dotted line). The Xystridura meraspid to holaspid transition (black dotted line) occurs later than Estaingia and so Xystridura meraspids grow to a larger size before the holaspid stage than do Estaingia meraspids. So the onset of maturity is delayed and the juvenile growth phase has been extended.

The largest Xystridura meraspid appear to have a smaller AF-EL/CL ratio than Estaingia meraspids, but the spread of data is large.

Obviously, the character itself - the distance between the back of the eye ridge and the occipital furrow - increases throughout growth in absolute terms, but that increase is at a slower rate that the overall growth of other characters, so the ratio decreases.

No lets look at what happens during holaspid growth.

Measurements of Estaingia and Xystridura.
Xystridura measurements adapted from McNamara (1981).

The first thing to note is that the meraspid growth pattern of reducing AF-EL/CL ratio is halted at the meraspid-holaspid transition. In the holaspid growth phase the AF-EL/CL ratio does not change with growth, which means that it is now increasing at the same rate as the length of the head. Also the spread of data at the meraspid-holaspid transition for Xystridura meraspid settles down in the holaspids suggesting that the timing of the transition has a bit of slop in it.

The second thing to note is that Estaingia and Xystridura have the same growth pattern - exactly the same growth pattern. Having a similar growth pattern could be chance - maybe this is a common growth pattern for trilobites. But having exactly the same ratio values is unlikely to occur by chance. This is strong evidence of an evolutionary relationship. Xystridura has inherited this particular ratio pattern and values from Estaingia.

Note also the "NSW Estaingia". This is Estaingia bilobata from Cymbric Vale in New South Wales. It is slightly younger than the Estaingia bilobata from the Emu Bay Shale. There are few measurements, but this form plots on the same trend and ratio values as the others - albeit a larger form than the Estaingia bilobata from the Emu Bay Shale.

Lets look at another character, this time the ratio of width compared with length of the head CW/CL

Measurements of meraspid Estaingia and Xystridura.
Xystridura measurements adapted from McNamara (1981).

Here again are the meraspid measurements for Estaingia and Xystridura. Again the character ratio decreases with growth. This means that as the head grows, the width is growing at a slower rate than the length. Also, the Xystridura meraspid growth phase is extended. This time however, there does seem to be some difference between the Estaingia and Xystridura meraspid growth phases. Unlike the last example, where the two growth patterns seemed to be in step. here the Xystridura meraspids appear to change the growth pattern. The larger Xystridura meraspids appear to stop the trend of decreasing CW/CL ratio and, by the time they reach the meraspid-holaspid transition, they appear to be slightly increasing the CW/CL ratio.

Things should become clearer when we look at the complete growth patterns.

Measurements of Estaingia and Xystridura.
Xystridura measurements adapted from McNamara (1981).

Here the growth patterns are markedly different. It should be pointed out that holaspid growth changes usually occur at slower rates than for meraspid forms, so that holaspid trends are less marked than meraspid trends. The Estaingia growth pattern shows that the reduction in the CW/CL ratio occurring in the meraspid growth phase is slowed at the meraspid-holaspid boundary. In the holsapid growth phase, the growth pattern shows that cranidial width continues to grow at a slower rate than cranidial length, but the difference between the growth rates is reduced somewhat.

However, for Xystridura, the apparent change in growth rate that occurs in the latest meraspids is carried into the holaspid growth phase, where the CW/CL ratio not only equalises (that is the width is growing at the same rate as length) but the width growth rate actually appears to be slightly exceeding the length growth rate.

Critically this change in Xystridura growth pattern occurs in the meraspid phase, but at the point where Estaingia would be expected to transition into the holaspid growth pattern. It isn't very clear in the graph (so click on it to enlarge) but the new growth pattern of the larger Xystridura meraspid after the Estaingia meraspid-holaspid transition (yellow dotted line) shows that the width is actually growing faster than the length (CW/CL ratio is increasing). At the Xystridura meraspid-holaspid transition (black dotted line) this growth rate actually slows down so that the width growth rate only slightly exceeds the length growth rate.

The NSW Estaingia actually plots between the Estaingia and Xystridura, suggesting that this change was underway by the time of Cymbric Vale sediments deposition.

The one thing that controls the cranidial width is the large bulbous thing in the centre of the head - the glabella. What these measurements are telling us is that during Estaingia meraspid growth, the glabella increases in width at a slower rate the the increase in the length of the head. During holaspid growth, the rate of growth of glabella width actually increases, but still not to the rate of increase of the length of the head - the glabella has increased the pace of its growth, but not enough to match the rate of growth in length the head is achieving - resulting in a slowing of the trend that is reducing the ratio of width to length, but not enough to stop the trend. In Xystridura, the glabella width actually starts to grow at a faster rate than the length - it is increasing in width ata faster rate than the head is growing longer - and so the ratio starts to increase.

If the glabella is changing size in one direction, maybe it's changing in another. Lets see.

The length of the head is composed of two measurements, the glabella. and the field in front of the glabella - the Preglabella Field (PGF) Any change in the glabella will affect the PGF. If the glabella increases in size at a faster rate than the length of the cranidium, then the PGF will reduce, if the glabella increases in size at a slower rate than the length of the cranidium, then the PGF will increase. If the glabella increase in size at the same rate as the length of the cranidium, then the PGF will remain the same. Measuring the PGF then, provides a proxy for glabella length growth.

Measurements of meraspid Estaingia and Xystridura.
Xystridura measurements adapted from McNamara (1981).

For Estaingia meraspid, the PGF is increasing with increasing meraspid size. This means that the glabella is growing at a slower rate then the length of the head resulting in an expanded PGF. By the Estaingia meraspid-holaspid transition, this pattern has stopped.

The Xystridura meraspid growth pattern follows the Estaingia meraspid pattern in showing an increase in the size of the PGF up to a certain point. Then, just before the Estaingia meraspid-holaspid transition this trend reverses, and the PGF reduced in size. This means that the glabella is now increasing in size at a greater rate than the length of the cranidium, resulting in a reduction in the PGF.

What does that mean for the holaspids?

Measurements of Estaingia and Xystridura.
Xystridura measurements adapted from McNamara (1981).

Lets take Estaingia first. After the meraspid-holaspid transition, the PGF ratio decreases slowly. This indicated that the glabella is growing at a faster rate than the cranidial length, so the PGF is getting smaller, but only slowly.

After the Xystridura meraspid-holaspid transition, Xystridura shows the same pattern of slowly reducing PGF and so slowly increasing glabella. But, as the Xystridura meraspid phase lasted longer, the trend to reducing PGF (increasing glabella) starts in the meraspid period and is accentuated. So much so that, by the time of the Xystridura meraspid-holaspid transition, the PGF is so small that even at the slowly reducing rate of the holaspid form, the PGF reached zero shortly after the Xystridura meraspid-holaspid transition. This means that the the glabella has been growing at such a faster rate than the cranidium, that it is so close to the front of the cranidium by the time of the meraspid-holaspid transition, that it quickly reaches the front of the cranidium early in the holaspid phase. PGF = 0.

Interestingly, the NSW Estaingia plot with the other Estaingia. This indicated that this change had not yet started by Cymbric Vale time.

All it took to produce a descendant form that looks significantly different from the ancestral form is the simple process of slightly delaying the onset of the holaspid phase, resulting in some of the slower holaspid growth pattern being incorporated into the faster meraspid pattern. In other words the large bulbous glabella of Xystridura is caused by a portion of the holaspid growth pattern being incorporated into the meraspid growth phase. "But wait a minute", you say (or you would say if you were paying attention) "the first character didn't change at all, and that involves the glabella - it measures the distance between the back of the eye ridge and the side of the back end of the glabella". That's true, but the growth of the glabella is focused towards the front of it. It is the front portion that has grown, not the back portion. So the back remains unaffected by the change.

Why is the glabella important? Well, that's where trilobites keep the stomach. So big glabella, big stomach.

So, what type of heterochrony is this? Go back to the list at the start and work it out.

I'll give you a clue. We have delayed maturity so the juvenile stage is extended. As a result, the the adult is bigger.

We are dealing here with Peramorphosis, and more specifically Hypermorphosis. One or more populations of Estaingia has evolved, by Hypermorphosis into Xystridura. An event that occurred around the Lower-Middle Cambrian boundary, during a time of eustatic sea level fall that would have reduced shallow-water living space.

The take-home message isn't that trilobites are cool (they are), but that this brings out a very important point about evolution, and a good refutation of the old creationist canard, "if evolution is true where are the half-way transitionals? The half reptile-half bird?"

What these results show, is that evolution doesn't happen to all features at the same time, or at the same rate, producing a neat half-and-half transitional form. Some features change relatively rapidly (the expansion of the frontal glabella), some features change relatively slowly (head width to length ratio), and some don't change at all (the distance from the back of the eye to axial furrow distance as a ratio of head length). So there isn't a transitional which has all features exactly half way between the ancestral and descendant forms. What we find are transitionals with a mix of features depending on the rates at which those features are changing. We should not expect to find exact half-and-half transitionals. Evolution doesn't work that way.

de Beer called it "Mosaic Evolution". That isn't an excuse for the lack of half-and-half transitionals, it's a description of how evolution operates.

McNamara, K.J. (1981) Paedomorphism in Middle Cambrian xystridurine trilobites from northern Australia. Alcheringa, 5: 209-224. DOI: 10.1080/03115518108567002

Palaeoporn 18

2010-09-26T13:47:00.017+10:00

It's not size, but form that counts.

Look, I'm sorry about this. It's quite embarrassing, I know. But in my defense, I have blurred the naked Dickinsonia at the top right of the slab so as not to offend any sensibilities.

Anyhow, on to the real subject of this Palaeoporn, the structure with the highly descriptive and emotive name - "Form D". Yeah . . . "Form D" . . . no, honestly!

The Form D is the . . . um . . . rather flaccid structure above the compass. Form D was the name given to a group of thick, long, trace fossils of unknown origin. While they are not common, it doesn't take much poking about to expose them.

Given the lack of structure it was hard to attribute a source for the traces (they are not ribbed for example) thus making it difficult to erect a reasonable phylogeny and nomenclature. So they got stuck with the name "Form D" - as they were the fourth type of trace structures to be catagorised. Recently, they are thought to be, not trace fossils, but body parts. They appear to be association with the form Phyllozoon.

Phyllozoon Hanseni (yellow arrows) and Form D (blue arrows)
from the Ediacaran of Canada.

Phyllozoon is a more-or-less bisymmetrical leaf-shaped structure composed of a series of 'tubes' which meet at a central zigzag suture. There seems to have been only one layer of tubes forming the 'vanes' of the frond, with a stiff outer covering. Numerous individuals are commonly scattered over bedding planes, sometimes overlapping. The fronds have obvious polarity (top and bottom) and their common association with Form D is too frequent to be chance. It is possible that Form D is actually the stolon to which the Phyllozoon fronds were attached. They may well have looked something like this below, except Phyllozoon probably wasn't green.

The alga Caulerpa taxifolia doing a passable imitation of Phyllozoon. Photo credit.

I suppose we should be grateful that Phyllozoon wasn't called Phallozoon . . .

Proterozoic Sponges Claim Doesn't Hold Water

2010-09-19T16:23:00.003+10:00

The geologic account of ancient life is plagued with reports that do not withstand critical assessment. This is a special problem in the older rocks, where reports of spurious records continue to dilute the authentic record of evolution on the primitive Earth . . .

. . . It is left to the reader to draw conclusions about similar instances not here alluded to; the record of alleged pre-Phanerozoic life is full of them.

Preston Cloud (1973)

Harsh perhaps, but Preston Cloud's words should be engraved on the cover of every Proterozoic geologist's field notebook.

Frankly, the Proterozoic is weird. Most of what you think is organic, isn't. The vast majority of the rest is microbial mats. And the stuff you really, really think could be metazoan, is usually microbial mats playing silly buggers.

I don't want to become a party pooper (and no that's not a plug for Bora's pootopia). I don't, I really don't.

I want to be able to yell and scream about some new find that pushes our knowledge of the early evolution of metazoans back well into the Proterozoic. I do, I really do.

But I can't.

In Nature Geoscience, Maloof et. al discuss possible sponge-grade metazoans from the approx. 640 million year old Trezona Formation in the Flinders Ranges of South Australia.

The Trezona Formation just underlies the Marinoan glacial deposits (dated to approx. 635 million years ago) which mark the final throw of the of the Cryogenian dice, and are overlain by rocks of the Ediacaran Period. The Trezona marks the onset of the Marinoan glaciation and contains shallow water stromatolite flake breccia and bioclast packstones filling gaps between stromatolite heads:

. . . we identified a great diversity of bioclasts. Most packstones contain clasts of probable microbial origin, such as spalled flakes of adjacent stromatolite laminae and ripped-up and rolled-up sediments with cohesion enhanced by the presence of microbial mats. However, many bioclasts have anvil, wishbone, ring, and perforated slab morphologies that are difficult to assign to an abiotic roll-up or bacterial mat origin. in addition, the red colour and calcite composition of these distinctively shaped clasts are unique to the packstones (and even packstone clasts entrained in the overlying Elatina Fm diamictite as far as 65km from the nearest Trezona Fm stromatolite reef outcrop) and are not found in situ in the layers elsewhere in the Trezona Fm that could have been brecciated and transported. Therefore we suspect that the 1-cm-scale red bioclasts represent the remnants of a community of organisms endemic to the stromatolite-packstone environment. (Maloof et.al 2010.)

This is what we are talking about

Outcrop photos from the Trezona formation showing the range of clasts
including "anvils" (d) and "perforated slabs" (g). (Maloof et.al 2010.)

2D thin sections show the clasts are composed of a mixture of opaque clays, quartz grains and micro-crystalline calcite, finer than the surrounding matrix, with a sharp, continuous contact with micritic rims

Thin-section photomicrographs from the Trezona formation. (Maloof et.al 2010.)
The authors then describe 3D shapes using serial sectioning (grid a bit off, photograph, grind a bit off, photograph). These 3D images show a three-dimensional network of 1mm diameter interconnected tubes. The tubes are also lined with micrite.

Three-dimensional reconstruction of the Trezona Formation
structures. (Maloof et.al 2010.)

So we have stromatolites with infilling packstones contain a diverse set of bioclasts representing chips from associated stromatolites and ripped up and rolled sediments that have been glued together by microbial mats. However, the paper claims that some of these bioclasts have shapes, include anvil, wishbone, ring and perforated slabs, that cannot be caused by nonbiological actions for the following reasons:

1) The shapes cannot be formed by rock chips
2) The red colour and micrite composition is unique to the deposits - no source of the chips can be found.
3) The micrite coating in the tubes and around the clasts may represent weakly calcified cell layers.
4) The interconnected 3D tube structures and the 3D symmetry support a sponge hypothesis

1 and 2
OK, lets split these up. The first two deal with the lithology and composition of the clasts. The authors say that the clast shapes produced cannot be formed from mud chips or bits of stromatolite, and that is true. It is also true that there are no lithologies similar in colour or composition to the clasts anywhere else in the Trezona Formation. This means that the shapes cannot represent chips eroded off earlier formed mudstones because there are nor similar lithologies or rock types in the area, and even if there were, rock chips cannot create the shapes seen. But there are problems with using that as supporting evidence for a biological origin. There are other explanations. Other abiogenic explanations.

The local explanation for the clasts is that they are mud flakes not mud chips, that is, not mud chips eroded off pre-existing rocks, but mud flakes formed when muds are deposited in ephemeral or short-lived deposits, such as ponds after flooding surrounding areas, or overbank deposits.

Drying mud Gammon Ranges. Photo Credit.

These muds settle and dry out and can form all sorts of shapes.

Drying mud, Canyonlands National Park. Photo by Douglas.

In some instances the mud flakes can completely roll up

Drying mud from Death Valley. Photo by Don Gale.

Check out one of the rolled mud flakes pictured above compared with a couple of the clast shapes

Clearly some mud flakes can take on the shapes that mud chips cannot, and can form some of the shapes present in the Trezona Formation that are being used as evidence for a biologic origin.

But it gets worse. See the arrowed clasts in the image with the "anvil" shape (at right). These are clearly mud flakes. They show a common curled profile that can be seen in the examples of recent drying muds above. Nor do they contain the tubes that are supposed to be a feature of the "sponge" clasts.

Now, here's the interesting bit. Both the obvious mud flakes and the "sponge" clasts are the same colour AND have the same composition (opaque clays and microcrystalline calcite, with the occasional very fine quarts grain - see photo-micrographs above) in other words your typical mud overbank deposit. Especially since the Trezona is pretty much a lowstand deposit (lower sea level). Some of the limestones deposited prior to the Trezona Formation, when sea levels were higher, are now exposed, providing a source for carbonate and putting some distance between the Trezona depositional environment and any non-carbonate source material (meaning that only very fine grained material is likely to reach the depocentre).

I think it is clear that the red clasts are mud flakes from overbank deposits, rolled up and redeposited between the stromatolites. In other words, waters carrying red carbonate mud, overtop riverbanks and settle into ponds. The mud settle out and the ponds dry up. The mud then dries, with the carbonate providing a good cement. The mud cracks, curls and eventually are dispersed by winds rain or floods into the nearby sea. The mud could be sourced from further inland on the Gawler Craton, and the carbonate sourced from limestones deposited during the period before the current regressive cycle, of which the Trezona Formation represents a lowstand or low sea level phase. The ephemoral nature of these overbank deposits, and their lack of lateral extent means that they do not contribute to the rock record, but dry out, crack, curl and are dispersed by wind and/or water. This also explains the occasional presence of "silica blebs" within the clasts. These represent very fine sand grains incorporated into the muds as they are deposited.

Clearly the mud flakes and "sponge" clasts have the same source - which is not organic. The shapes and colour cannot be used as supporting evidence of an organic origin for the clasts.

The authors suggest that the red matrix could be a replacement:

Alternatively, the original organic skeletons could have been coated in a bacterial extracellular polymeric substance following their death. The chemical composition of the Fe, Na, K clays found in the Trezona Fm bioclasts is similar to that of augenic minerals precipitated by microbial biofilms during the replacement of soft tissues. The extracellular polymeric substance would have also formed a template for abiotic calcium precipitation. (Maloof et.al 2010.)

Now if I'm reading that right, it looks like the authors are suggesting that the original skeleton of the "sponges" has been replaced by the red mud, since there is no evidence for spicules or any other type of a primary skeleton.

There are two problems with this explanation for the absence of a primary skeleton. The first is the fact that the red matrix composition is shared with clasts that are clearly mud flakes. The second problem goes to number three in their list of supporting evidence, that the micrite coating in the tubes and around the clasts may represent weakly calcified cell layers.

3
The authors comment that the "sponge" clasts are surrounded by a micrite rim (the dark outer rim around the clasts in the photo-micrograph at right. I don't know why they don't use the standard terminology - micrite envelope), which is also present lining the tubes. They suggest that:

the micrite of uniform thickness and texture coating both the exterior surface and interior canal walls could represent weakly clacified cell layers sandwiching the mesohyl of a sponge grade organism. (Maloof et.al 2010.)

To their credit the authors then demolish this argument by pointing out that:

However, texturally similar (but less uniform thickness) micrite also coats peloids that do not seam to be part of the Trezona Fm organisms.

Yes, that's a bit of a problem. It's a bit difficult to suggest that the micrite envelopes are evidence of mesohyl when almost everything in the deposit has them.

Micrite envelopes are well known and are generally considered to be formed from filamentous organisms (bacterial, algal or fungal) who's filaments calicify and coalesce into a intertwined mesh around the clasts. In this case the areas between stromatolites are colonised by numerous filamentous organisms that grow around all the clasts present and eventually form the micritic envelopes. So having micritic envelopes around the "sponge" clasts and within the tubes cannot be used as evidence of sponge-grade tissues.

But there's another problem.

As stated above, the authors suggest that the mud matrix could be a replacement for the original skeleton structure around the tubes. The presence of the micrite envelopes is really problematic here. The authors comment that:

However, the contact between micrite coating and mixed clay-chert-calcite interiors is usually sharp, with no evidence of diffusive or porosity-following micritization. (Maloof et.al 2010.)

This means that any replacement of the original skeleton must have occurred prior to the micrite envelope being laid down. However, the tubes must have been sealed during replacement as there is no replacement material in them. After replacement, the tubes must have opened again to allow the micrite envelope to form.

Unlikely.

The evidence suggests that the red matrix is not a replacement, but a primary feature.

4
Which brings us to number 4, that the interconnected 3D tube structures and the 3D symmetry support a sponge hypothesis. I'll say up front that I do not know what the tubes are. They could be sponge tubes, but the evidence for that is equivocal at best.

A more likely explanation is that the "sponge" clasts are mud flakes that have been coated by filamentous organisms, rolled around and glued together. The tubes would then be where the filamentous outer coating of individual clasts, acting as a buffer and holding the clasts apart as a number of clasts were bound together.

It is interesting to note that an analysis of similar lithologies from rocks of the the equivalent Cryogenian interval south of Adelaide found;

. . . a light greyish microcrystalline limestone in which numerous flakes of grey calcareous mud are set. The flakes are typically intraformational and a gradation is noticed from intraformational breccia to edgewise conglomerate. Most of the flakes are flat, but there is a tendency to turn at the edges; length varies from several to 20 mm. in thin section or on polished faces there is a superficial resemblance to annelids (reference), but this is quite lost when the third dimension is considered. (Sprigg 1942)

In the Proterozoic, weirdness rules. This makes interpretation difficult. I don't think the evidence presented in the paper is enough for a sponge interpretation to hold water. However, we've been misinterpreting the Proterozoic for some time, and the authors are in good company.

Cloud, P. (1973) Pseudofossils: A Plea for Caution. Geology, v. 1, p. 123-127.

Maloof, A., Rose, C., Beach, R., Samuels, B., Calmet, C., Erwin, D., Poirier, G., Yao, N., & Simons, F. (2010). Possible animal-body fossils in pre-Marinoan limestones from South Australia Nature Geoscience, 3 (9), 653-659 DOI: 10.1038/NGEO934

Sprigg, R.C. (1942) The Geology of the Eden-Moana Fault Block. Transactions of the Royal Society of South Australia, 66(2), 184-214. Download

Please Give to DonorsChoose

2010-09-09T18:07:00.003+10:00

OK I'm back and finalising a couple of posts. In the meantime DonorsChoose is running again.

DonorsChoose.org is an online charity that makes it easy to help US school students in need. (Yes I'm Australian, but this is important.)

American public school teachers post classroom project requests on DonorsChoose.org. Requests are for arts, science, music, language, civics, sports, etc.

You can browse project requests and give any amount to the one that inspires you. Once a project reaches its funding goal, the materials are sent to the school.

Education is important. If you have a few dollars to spare please consider supporting teachers trying to give their students a good education.

A number of the projects are close to being fully funded, a few dollars could make all the difference.

We've Lost Cedric

2010-09-01T18:06:00.003+10:00

Cedric the Tasmanian Devil has been put down.

Cedric was at the forefront of research into the deadly Devil Facial Tumor Disease, which at last estimate was infecting 60 per cent of the wild devil population in Tasmania.

He made waves in 2007 when he was injected with a strain of DFTD and survived. He even survived a second strain with only a couple of minor tumours, which were removed.

Cedric had shown an immune response to the disease, and was otherwise healthy. It was hoped that he would lead researchers to a treatment or vaccine for the disease, but an X-ray last week showed a number of tumours in the lungs, and it was decided to euthanase the 6-year-old Cedric.

Damn.

Donations to help the Tassie Devils can be made here.

Cutticcini's Profile Enlargement

2010-08-31T18:04:00.004+10:00

The wingnut Virginian Attorney General Ken Cuccinelli has had a setback in his witchhunt of Professor Michael Mann. Cuccinelli was asking for all documents from the University of Virginia concerning professor Mann's research while at UVa, to "investigate" any possible fraud committed by Professor Mann in his grants received to study climate change. A judge has ruled that Cuccinelli failed to show a sufficient “reason to believe” that UVa possessed any documents related to Mann that suggested a fraud occurred. Cuccinelli will continue harrassing UVa and Mann on the taxpayer's dime.

Cuccinelli is a climate change denier, who has also directed all state schools and colleges to remove sexual orientation references from their non-discrimination policies (in other words removed discrimination protection for gays and lesbians), and sued over the constitutionality of federal health care reform. All on the taxpayer's dime.

Cuccinelli is doing nothing more that using taxpayer money to fund a major profile enlargement, which is odd given his opposition to publicly funded healthcare.

Evolution Among the Trilobites Part 1

2010-08-15T15:22:00.002+10:00

The last Palaeoporn featured the growth stages of meraspid, or juvenile, Estaingia. This post will use those meraspids and a bunch of holaspids, or adults, to measure the growth patterns of Estaingia, or it’s ontogeny.

Why? Because it’s important. It allows us to plot the growth patterns and if you know the growth patterns you can used them to look at evolutionary relationships.

If you want to look at evolutionary relationships between species there is one, and only one rule.

Ya gotta know what the kids are doing.
If you don’t know what the kids are doing, you can get, as some vertebrate palaeontologists are now finding, evolutionarily embarrassed. Ontogeny can provide clues to evolutionary relationships.

Studies of ontology requires the measurement of various features to show how they change with time or size (usually the two are interchangeable – in trilobites anyway). The changes in one feature are then compared with changes in another.

At right is the head of an average trilobite showing which bits are which. This post will be concerned only with the head and what happens to it during ontogeny. Actually its even more restricted than just the head. We'll only be looking at the cranidium. That's the central area including the bulbous glabella. Why? well we need to take a bunch of measurements over a range of specimens to build up a picture of the changes that occur during ontogeny. The trouble with the librigene or free cheeks is that they are, well . . . free, and tend to be lost (as pointed out in Palaeoporn 14 and 16). The cranidium is usually left behind and so is a better subject for measurements.

At right is a cranidium of an Estaingia. The relevant measurements that we are interested in are marked. CW is cranidial width, which is literally the distance between the eyes. PGF is Pre-Glabella Field which is the area in front of the large bulbous glabella. (Incidentally the pre-glabella field only runs to the shallow trench towards the front of the cranidium. In front of the trench is the doublure. That is folded underneath the cranidium in life, along the trench, and pops up during moulting (see Palaeoporn 16). GL is the glabella length. Adding PGF and GL gives us a value for the length of the craniduum. POG is Pre-Orbital Glabella which is the bit of the glabella that lies in front of a line drawn between the front tip of the eyes. AF-EL is the distance between the end of the Axial Furrow (the trench behind the glabella and the back tip of the Eye Lobe.

Lets show some measurements - the length of the central portion of the trilobite head, the cranidium, compared with the width of the cranidium, and the length of the glabella, for each specimen, as seen below
Here the measurements fall on a straight line. This is called isometric growth, where the ratio of the two features does not vary with growth. In example A, the ratio of the length of the cranidium to the width of the cranidium does not change with growth. In example B the ratio of the cradidial length to glabella length does not change. So during isotmetric growth there is no change in the shape. (What? Yes, OK, example A is not strictly isometric, since isometric growth always passes through the origin and a line drawn through the plot in A doesn’t. Just. But trust me, compared with what’s coming up next it’s pretty much isometric.)

Isometric growth can be very useful in confirming that specimens belong to a particular species. In the examples above, the red dots represent meraspid Estaingia and the blue dots holaspid, or adult forms. The fact that they all line up on a straight line is supporting evidence that the meraspids do belong to Estaingia. This is important because species are defined by a “type” specimen which is normally an adult, and so it can be quite difficult to place meraspids in the correct species if the growth patterns vary considerably from the adult.

Oh yes, the black dots at the far end of both graph trends represents a holaspid Estaingia from a different location and a slightly younger deposit, at Cymbric Vale in New South Wales (NSW Estaingia). Thought to be the same species as E. bilobata discussed here from the Emu Bay Shale, but also though not to be for a couple of reasons. It'll feature later but see how it plots along the same trend as the other specimens? good evidence that it is E. bilobata, but I'm getting ahead of myself.

Frankly, however, isometric growth while it has it’s place, is a bit boring. Meraspid 1 looks pretty much like the adult form. (no problem in putting the meraspids in the correct species there then.)

Just as well then that not all growth is isometric. In fact most growth patterns are not isometric, but anisometric. Anisometric growth, as you may suspect, is where the ratio does not remain constant, but changes during growth, and so shape changes during growth. Which means the meraspid can look distinctly different from the holaspid.

Holy rotating vectors Batman!
Now it gets interesting. There is only so much you can do with straight lines. Everything is better with curves! Anisometric growth changes are not random. They don’t occur because the merasid didn’t like the look of itself in the mirror. The represent hereditary traits. In the two graphs above, A shows Cranidial Width against Axial Furrow to posterior of Eye Lobe (as a percentage of cranidial lenght) (CW/AF-EL) and B shows Cranidial Length against Pre-Glabella Field (as a percentage of cranidial length) (PGF/GL+PGF).

Here the difference in growth patterns between the merasipd and holaspids is marked. This is telling us important information about how the final look of the holaspid form is achieved, and what pattern of growth occurred.

In graph A the feature being measured is the curvature of the eye. In early meraspids, the eye curvature is quite shallow and so the lower end of the eye is a significant distance from the Axial Furrow. As the meraspid grows, the eye curvature becomes more pronounced and the distance between the lower end of the eye and the axial furrow decreases. At the end of the meraspid stage, the distance (as a percentage of cranidial length) is around 0.25. In the holaspid stage this trend ceases, the eye reaches its maximum curvature, and doesn't change again, so the value remains at around 0.25. The NSW Estaingia plots along this holaspid trend albeit at a larger size that those at Emu Bay, but again, it is good evidence that NSW Estaingia is Estaingia bilobata.

In Graph B the preglabella field as a percentage of total cranidial length is plotted against cranidial length. Here the trends are different. In the meraspids, the preglabella field increases with growth until the Holaspid stage is reached. Then the trend is reversed and the preglabella field begins to reduce in size with growth, albeit at a slower rate than the meraspid rate. The NSW Estaingia again plot on the holaspid trend for Estaingia bilobata providing more evidence that the NSW Estaingia is E. bilobata.

One last graph which shows the preorbital glabella or POG (the portion of the glabella in front of the eyes).

Note that this is a mirror of the pregalbella field plot, and provides an explanation for the pregalbella field changes. The preorbital glabella in the meraspids decreases in size relative to cranidial length. In other words, as the cranidium increases in size, the preorbital glabella is increasing at a slower rate. This means that the area in front of it has to increase in size. So the increase in the pregalbella field we saw in the previous chart is a result of the preoccular glabella not keeping up during meraspid growth. However, in the holaspid stage, this trend is reversed and the preoccular glabella starts to grow at a more rapid pace than the cranidium generally, and begins to represent more and more of the total cranidial length. Thus the preglabella field begins to decrease as a proportion of the total cranidial length. Once again the NSW Estaingia plot among the Estaingia bilobata and along the trend. We can say with some confidence then that NSW Estaingia is a larger version of Estaingia bilobata.

Next time how these growth plots can provide information on evolutionary relationships.

2.1 Ga Multicellular Colonial Organisms - Update 2

2010-08-07T12:05:00.009+10:00

In posts here and here I discussed why I thought the 2.1 Ga structures from Gabon, figured in the Nature paper, were actually microbial mats and not examples of multicellular colonial organisms.

I now have some further info which strengthens my view. I'd like to thank Dr Diana Cuadrado of the Instituto Argentino de Oceanografía who very kindly sent me some more images of microbial mats.

This mainly revolves around the claim in the paper that microbial mats . .

. . often leave characteristic in carbonate ad siliciclatic rocks. Such structures, however, including those formed in shales and mudstones, do not resemble the Gabon fossils". (p. 103)

As I've discussed previously, I disagree.

At the top of this post is an example of a modern microbial mat (top image), compared with a photo of the 2.1 Ga structures (bottom image). The black box in the top image represents the area of the lower image at the same scale (The bar scale is 10 cms in the top image and 1 cm in the bottom image). This reinforces just how small these 2.1 Ga structures are.

Here then, is more evidence that microbial mats can produce the structures seen in the 2.1 Ga specimens.

Here is a close up of a large gas bubble in a modern microbial mat (it was taken last week - you can't get much more modern than that!). As you can see by the comparison with one of the 2.1 Ga specimens at the same scale, gas bubbles in microbial mats are on the same scale as the 2.1 Ga specimens.

For me this is the clincher (if a clincher were needed)

The top photo is of a modern, ruptured gas bubble, the bottom is of a 2.1 Ga specimen. See how the modern microbial mat is flexible enough to fold and stay intact even when torn. But, see the folding to the top and right of the hole. It's almost an exact match for one of the 2.1 Ga specimens figured, to scale, below. No that's not quite right . . . it's an exact match!

Not only that but there is a small fringe beyond where the folds end in the modern example, similar to that seen in the 2.1 Ga specimen.

To say something like "Ta Da" at this point would be churlish, juvenile and unprofessional, . . . so

TA DA!

But wait, there's more.

This is a photo of a mature microbial mate with a couple of overturned pieces. Not the cracking in the larger piece around the margin. his may be the cause of the "radial fabric" of the 2.1 GA strucutures. The smaller piece has even more marked cracking and looks similar to this 2.1 Ga specimen below.

This latest evidence strengthens the argument that the 2.1 Ga structures are pyritised microbial mats and not multicellular colonial organisms.

Palaeoporn 17

2010-07-29T21:48:00.030+10:00

Meraspid
Drumming
You never forget your first. The time. The place. The moment.

The windswept coast. The bed that refused to cooperate. A cleavage that simply wouldn’t quit. But then suddenly, everything is revealed. The curves! So different. Stood out in the crowd despite being petite. I couldn’t fail to see, even at a distance of 4 feet.

No, you never forget your first. First meraspid that is.

This fellow is a personal favourite of mine. It’s a meraspid (or juvenile) Estaingia bilobata It was the first meraspid found at from the Emu Bay Shale. It’s a stage 10 meraspid. Thanks to it, and other merasipds found in the Emu Bay Shale, we can work out the ontogeny or growth pattern of Estaingia, and as an added bonus allows us to work out some evolutionary relationships (but that’s for another post).

This Palaeoporn is all about ontogeny amongst the trilobites, more specifically Estaingia.

One of the great things about trilobites is that, to grow, they have to moult the hard exoskeleton. This means that one trilobite can leave behind a complete growth history in moults. Since this is unlikely to happen for one, many trilobites of the same species leaving moults behind allows us to build up a picture of the growth pattern in a way that we simply can't do for moult-challenged organisms.

Meraspids are what trilobite larvae grow up to be before they grow up to be adult trilobites. Trilobite larvae, or protaspids look like just a head. Suddenly things get serious and the protaspid gets a tail. Or at least the beginnings of one. A furrow appears towards the back of the protaspid, which will separate the tail or pygidium from the head or cephalon. Once the furrow is complete, the trilobite is considered to have moved into the meraspid stage - meraspid 0. 0 because it has no thorax segments yet. Just a head and a tail.

Once in the meraspid stage, the trilobite begins to add segments to the thorax, usually one per moult, but in some species this can be more. Each meraspid degree or stage is represented by the addition of another thorasic segment and is numbered according to the number of segments.

The specimen at right (Fig. A) is a Meraspid 1, the smallest meraspid so far found at Emu Bay.

The most striking thing (apart from it's size - the white scale bar represents 1 millimetre! Hence it's a bit blurry) is the spines. In very small forms spines become important. If meraspid 1 was swimming amongst the plankton, the spines would help with buoyancy, helping keep the meraspid afloat. If the meraspid was on the sea floor, then the spines would help keep the meraspid from sinking into the mud. We don't know if Estaingia meraspids were planktonic or scurried around on the sea floor. The spines may also provide some defense, but the get smaller as the meraspid grows so it doesn't appear that defense was a primary function. In meraspid 1 the one segment has a pair of large spines, as well as a pair of backward pointing spines on either side of the head. Meraspid 2 would have had two segments each with a pair of long spines.

As the meraspid grows, segments are added from the front of the tail. We can see this in meraspid 7 at right (Fig. B, scale bar 1 mm). This has 7 segments, but the two original segments with the spines can be seen at the front of the thorax, with the non-spiney segments, which have been added later, positioned behind these two. If the thorasic segments were added from the back of the head, then the first two segments with spines would be at the back of the thorax next to the tail. The large spines on the head are also still very visible.

In Meraspid 10 at right (Fig. C, scale bar 1 mm) things are starting to change. The first thing to notice is that the large spine on segment 1 is almost gone. There is a much reduced spine there. Also the spines have become more curved. They are still long though - still the length of the meraspid. The head is very well preserved and provides a wealth of information on the way the various elements of the head change with growth. The rounded shape and the spines are very distinctive. Nothing else in the fauna is like that. So, even though it's only a few millimetres across, it immediately caught my eye.

Finally we have meraspid 12 (Fig. D, scale bar 1 mm). We are almost at the Holaspid stage or mature stage, of 13 segments, and the meraspid is now similar to the final adult shape. Note that the second thorasic spines are much reduced, and the spines on the head are also beginning to reduce in length. The thorasic spines will completely disappear in the adult, and the spines on the head will be reduced, but still present.

And this at right is a fully mature Estaingia. You can see that the thorasic spines have gone, and the spines on the head are much reduced.

Below is a diagrammatic representation of the ontogeny of Estaingia featuring the four meraspids figured above.

It gives you a better idea about what changes are occurring as the trilobite matures. Features to look out for are the relative width and length of the head and the glabella or central bulb region of the head. This is important because these relative values can be plotted and, as they remain at a constant ratio can help confirm the identification of the meraspids with the holaspid form. Like so:

This is a plot of the length of the longest part of the head (cranidium) against the width from eye to eye, and the longest part of the head against the longest part of the glabella - the central bulb area of the head.

As you can see the meraspid measurements (in red) line up along the same trend line as the adults (in blue) giving us a high degree of confidence that the meraspids are of Estaingia. Also notice that the measurements are clustered - i.e. not evenly distributed. This represents the moulting habit of the trilobites. As growth can only occur once the trilobite has moulted the pattern of growth is stepped. Unlike a constantly growing form, where the plot would be more even.

Using measurements of growth patterns can be very useful because with some trilobites, varying the time spent in particular growth patterns as can dramatically alter the end result - or what we call evolution. But that's for another post.

Informed about Introns

2010-07-26T18:15:00.003+10:00

Stephen Matheson has a series of posts about introns and their misuse by the Disco 'Tute.

Genes are transcribed into RNA for shipping out of the nucleus to make proteins. Introns are areas of the RNA that have been transcribed from the gene but are then removed from the RNA template prior to it moving out of the nucleus.

It all about the junk - or not-junk.

Go read Steve's posts Part I, Part II, and Part III, and get informed.

Palaeoporn 16

2010-07-22T22:43:00.007+10:00

Extreme Ecdysis

When you're broken, in a million little pieces . . .
You may want to check out Palaeoporn 14 and 15 before reading this as Palaeoporn 16 follows on from them. That's ok. We'll just talk amongst ourselves until you get back.

So . . . where are you from? . . . Fort Saint John, Canada? Really? Good ol' Highway 97. . . . umm, come here often? . . .

Oh, ok you're back. Right. First thing, you need to see this video of a giant spider crab moulting (hat tip PZ)

Once you've seen it and read PZ's piece on moulting, or ecdysis. The linked video of a spider crab moulting in PZ's piece is the one featured here. Very instructive, if not a little creepy. But remember that trilobites - being proper arthropods - exited the old body exoskeleton old school i.e. head first, not arse first like a common chelicerate.

Ok, now we have an idea of what ecdysis is, this Palaeoporn is an example of what happens when things go wrong . . . very wrong.

The photo at the top is of the trilobite Redlichia takooensis, or rather what's left of one after a particularly difficult mould. Just to remind you, at right is what a Redlichia takooensis should look like. R takooensis is a Lower Cambrian trilobite with a 15 segment thorax and small pygidium or tail. A major characteristic of R takooensis are the large spines, on either side of the head, at the back of the head in the centre, and two large spines on the axial rings of segments 6 and 11 (counting back from the head) (What? Axial ring. The middle part of the thorax. What? Thorax. The middle part of the animal between the head and the back end (pygidium). What? Yes the pygidium is very small, it's a micropygous trilobite. What? No. The division head-thorax-pygidium is not how the trilobite got it's name. The "three lobes" refers to the three zones of the thorax, the plura on the left, the axial ring, and the plura on the right).

There are probably spines on each axial ring, but 6 and 11 have the biggest. The spine coming off the rear of the trilobite, seen in the photo (above right), is from segment 11 - so the spines were pretty long.

To give an idea of what R. takooensis looked like I'm going to cheat an use another trilobite to approximate Redlichia.

Left side view of Paradoxides masquerading as Redlichia (it's got three extra segments - no, don't count them!). Thick line represents facial suture. (adapted from Whittington 1990)

Notice the spines. These will be very important in what happens in extreme ecdysis. In life, the spines would have not sat flat along the thorax, but would have been mobile and could be moved in an arc, from flat along the body (as above and in complete trilobite photo above right), through some acute angle (as seen in the ~~Para~~Redlichia diagram above).

What you don't see is the series on notches on the back margin of the first 5 segments of the thorax. These would have acted to lock the first 6 segments in place making this portion of the thorax act as a rigid body. That's also important.

What's also important is that the trilobite could bend. It could flex into an arc - though not into a ball like later trilobites (an important feature for Anomalocaris as discussed previously). Also the maximum flexure occured around segment 5.

OK, ecdysis in Redlichia. Normally Redlichia would have operated in a similar way to Paradoxides shown below.

Maneuvers during exuviation of Paradoxides 2. Left side view, thick line on head represents the suture line. 3. Flexure of body. 4. Front view showing open sutures and animal beginning to emerge (stippled). 5. Side view of animal beginning to emerge. (Whittington 1990).

The trilobite arched upward, planted the front of the head in the sediment and pushed using the back end as a brace. This put pressure on the head and the sutures around it. These part, with the cheeks on either side parting from the central area of the head, and the front part of the head separating and lifting upwards. This allowed the soft new body to emerge through the front of the head and 'head' off, leaving the cast of exoskeleton behind.

There is one difference (alright two). The spines. These could have been brought into play if the old exoskeleton didn't play ball, as shown below.

Here, the rear spine could have been used as a lever to apply more pressure on the head sutures, forcing them to separate and allow the trilobite to exit. How do we know this? well, a) it seems like a reasonable thing to do, and b) we have the specimen figured as Palaeoporn 16 (and others).

Let's remind ourselves of the specimen, 'cos its been a while.

What we have here is one disarticulated trilobite. There is a split in the thorax between segments 4 and 5, and another between segments 10 and 11. The thorax has been split into three pieces, comprising segments 1-4, 5-10, and 11-15 (plus pygidium).

Which brings us to a very important question. Where's the head?

The left free cheek is there, roughly where it should be at the front end, but it's inverted. It's inside out. Flipped over. The nice curved margin you can see is actually where it joined the eye. But the rest of the head?

Well, most is missing, but see the white and orange line running away from the free cheek and pointing to the 2 o'clock position? That's what's left of the head. It's the lower part of the head, basically a thin band of exoskeleton (called the doublure) which runs around the underside of the head and attached to both free cheeks and the front of the central portion of the head (the doublure is show in black at right). That central top portion of the head is gone, but the doublure is rammed into the sediment and twisted.

To give you some idea, here is a somewhat stylised diagram to illustrate.

What we have is one very sad and sorry trilobite. But, knowing what we know of ecdysis in Redlichia we can piece (Ha!) together what happened.

Knowing that the first 6 segments could lock together, and and the spine on segment 11 was used as a pivot point, simple mechanics tells us the the maximum forces exerted at or around segment 5, (where the maximum curve would be - the locking of segments 1-6 would re-enforce this), and around segment 11.

So, the trilobite arched up, rammed the front of the head into the sediment and braced with the spine on segment 11. Nothing happened.

Eventually the arching and the bracing built up so much pressure that something had to give. In very quick succession, the exoskeleton behind the head went (we know this can happen from Palaeoporn 15), as did the sutures on the head. But also the pressure acting on segment 5 became too much and the exoskeleton ruptured between segments 4 and 5. Also to pressure around segment 11, caused by bracing against the spine, causes the exoskeleton to rupture between segments 10 and 11.

The trilobite exited the broken exoskeleton, probably taking the middle portion of the head with it. That left the free cheeks separated from the central head exoskeleton, but still attached to the doublure, which was buried in the sediment. The left free cheek, still attached on its outer side, rotated outward to lie inside out, while the other is buried.

Tough moult!

But there's more. Here's another example. Similar story with similar results (sorry it's in black and white. I could say it's in black and white for the ambiance, but I just don't have a colour photo of it).

This time the thorax exoskeleton gave way behind segment 6 and behind segment 11. And this time we have the head. And both free cheeks, but they are inverted an displaced slightly. Also the doublure is present. it's the thick band right at the front of the head.

This is a classic example of a broken, incomplete, trilobite providing more information than a perfect specimen would. They provide information on trilobite activity and mechanical information on the exoskeleton.

They also provide a whole new definition of the term "growing pains"

Whittington, H.B (1990) Articulation and Exuviation in Cambrian Trilobites. Phil. Trans. R. Soc. Lond. B. Vol. 329 no. 1252. pp:27-46 doi:10.1098/rstb.1990.0147

Never Listen to the Weather Forecast

2010-07-19T21:32:00.005+10:00

Never listen to the weather forecast.

The forecast of an impending heavy thunderstorm.

An impending heavy thunderstorm that threatened to overflow your blocked gutters.

The gutters you decided to clean with the help of a ladder.

The ladder you don't secure well enough so that you fell off.

A fall of about 15 feet to the ground.

The ground from which your housemate had to drive you to hospital.

The hospital where you stayed 10 days.

Ten days in which they scraped together what's left of your elbow.

The elbow that needed a metal implant to function and so looks like this.

(A metal implant that doesn't set off the metal detectors at airport so that you can't even look at the security people and nod and say 'yeah, that's me')

A metal implant which required 8 months of physio come rain or shine.

The rain that reminded me of that forecast heavy thunderstorm that NEVER CAME.

So yeah, never listen to the weather forecast.

On the up side, I can now get all my images (x-rays, CT) on a cd which I can keep and upload to the internet!

2.1 Ga Multicellular Colonial Organisms - Umm, Not (update)

2010-07-13T21:50:00.005+10:00

I previously discussed why I don't think the 2.1 Ga structures found in Gabon are multicellular colonial fossils.

Having looked at the Nature paper some more, another thing springs to mind.

Scale.

Here are some of the structures as figured in the paper.

Note the scale bars against each example. Those scale bars represent 5 mm! That's right millimetres!

These things are small. Especially the central area that contains the folding.

Now, compare that with the examples of bubbles in microbial mats

Photo from Cuadrado and Pazini (2007)

There is no scale, but some of the bubbles must be at least the size of the central folded area of the specimens figured in the Nature paper. This means we have structures documented today in microbial mats that equate in size to the central area of the structures from Gabon.

Now, what would happen to a gas or fluid filled bubble if it were covered with sediment and the gas/fluid escaped? It would deflate. Not deflate flat, as the microbial structure would be too thick. Maybe it would fold on itself just like the central structure in the specimen in row two above? Especially if there was an encouraging push from overlying sediment.

I'm even more convinced that the Gabon structures are microbial mats.

UPDATE 2

Diana G. Cuadrado and Natalia V. Pizani. (2007) Identification of microbially induced sedimentary structures over a tidal flat. Latin American Journal of Sedimentology and Basin Analysis. v.14 n.2 La Plata ago./dic. 2007

2.1 Ga Multicellular Colonial Organisms - Umm, Not

2010-07-05T22:36:00.040+10:00

2.1 GA structures on black shale bedding surface. Scale bar 1 cm. (El Albani et al. 2010)

The latest edition of Nature has a paper claiming 2.1 billion year (Ga) old multicellular colonial organisms from Gabon. This is a remarkable claim, since the oldest definitive large multicellular organisms so far found in the fossil record are from less than 600 million years ago (It is still not certain if the 2 Ga Grypania spiralis is a eukaryote or large bacterial colony). So remarkable is the claim in fact, that it made the front cover of Nature.

I think they are wrong.

Lets be more specific here. There are two claims - that the structures are 2.1 Ga old, and that they represent large multicellular colonial organisms.

First the date. That appears well constrained. Chris Rowan has good coverage of the dating at Highly Allochthonous, so I have no argument against the age.

I don’t think they are multicellular colonial organisms. I think they are pyritised remains of microbial mats, or structures associated with microbial mats.

There’s been ample coverage of the paper, but I want to concentrate on the reasons why the authors think that the structures represent organised colonial organisms.

The structures are found in unmetamorphosed black shales. Over 250 specimens have been recovered. They are pyritised and embedded within the sediment. They range from 7-120mm in length, 5-70 mm in width, and 1-10 mm thick. They can occur in densities of up to 40 specimens per square metre, at random orientations, but all are horizontal to bedding. All are wrinkled to some degree, with some having large central pyrite nodules. Some show significant folding. All show radial cracks. The authors used micro-computed tomography (Micro-CT) to produce three-dimensional images of the structures. They also undertook carbon and sulphur isotope analyses of the host rock and the structures.

On the following lines of evidence the authors decided that the structures represented multicellular colonial organisms:

The structures shown under Mirco-CT are not the same as produced by microbial mats.

They are unaware of any inorganic process that could produce the folding patters seen in the structures.

The folding suggests an originally cohesive flexible sheet.

They are unaware of any inorganic process that could produce the radial fabric seen in the structures.

The radial fabric represents peripheral accretion of flexible organic matter.

The 12C/13C carbon isotope ratio in the host sediment is different to that in the structures suggesting the structures represent distinct organisms.

Steranes have been found in the shales, a compound associated with eukaryotes.

A lack of support for any other inorganic origin.

I think pyritisation of microbial mats is a better explanation. Here’s why.

I’d like to take 1, 2, and 3, together because they all relate to the physical properties of microbial mats.

First let's take a look at what we're talking about.

Micro-CT-based reconstructions and virtual sections of four specimens from the FB2 member of the Francevillian Group. First Column - original. Second column - volume rendering in semi-transparency. Column 3 - Transverse two-dimensional specimen. Column 4 - longitudinal section running close to estimated centre of specimen. Scale 5 mm. (El Albani et al. 2010)

The structures are pretty much all pyrite. The absence of pyrite is marked by the radial cracks. The bright central area in rows 3 and 4 represent a central pyrite nodule. This is not present in all specimens. This is important, as the large thickness values for specimens are all associated with this central nodule. Away from the nodule, or when a nodule is not present (e.g. row 2 above), the structure is a thin film of pyrite around 1-2 mm thick.

This is really important. All the folding is just that, folding. The apparent holes (black areas) in the images above do not represent complex structure within the specimen. The image is a slice through the specimen at a certain level. Where the pyrite film is folded below the level being imaged (downward folds), or completely above it (upward fold), you get a black space. The images appear to show complex structure, but it is simply a line drawn across an undulating surface. There is no internal structure here other than the radial fabric.

Further, and critically, the authors have concluded that the thin pyrite film and the central nodule represent different periods of pyrite formation. This is supported by sulphur isotope data, and I am happy to accept their conclusion.

This means that the large nodules have little to do with the original structure of the specimens, and, in fact they appear to occupy a central cavity in the specimen when they are present. An example of an actual nodule is below.

Section through a specimen showing central pyrite nodule surrounded on both sides by sheet material. Scale bar 1 mm. (El Albani et al. 2010)

In this specimen you can see that the nodule and the thin film on either side of it is almost all pyrite. The gaps in the center of the nodule are unexplained, but probably host sediment. Ignore the pretty colours. that refers to sulphur isotope analysis which I'm not questioning.

So, if we ignore the central nodules for the present, we are left with an original structure that is a thin film approx. 1-2 mm thick which has been thrown into folds in some specimens (e.g. row 2 above) but not in others (e.g. row 1 above).

The authors claim that the folding and the radial cracks cannot be accounted for by inorganic processes. I think they can.

Look! over there on the right! Is a 2.1 Ga colonial organism with a radial fabric? Is it a Proterozoic jellyfish? No, it's . . well, I'll explain later. But compare this example with rows 2, 3 and especially 4 of the Micro-CT images above. Notice that it has a central zone which is distinct from the periphery. Notice there is a faint dark band separating the central core from the periphery. Notice also the distinctive radial 'cracks' that spread out from the core Central mass? Check, radial cracks? Check. This would appear to be a good match to the 2.1 Ga structures.

But if you are not convinced, here's another variety of the same structure. this time we'll compare it directly with row 2 above as this has the best fold structure presented.

Can you see the fold pattern at the centre of the lower photos? It's quite similar to the fold pattern in the Micro-CT image. These images are of water escape structures in Ediacaran sandstones. The difference in colour you can see is due to the sandstone being deposited wet and dirty - i.e. waterlogged and with a significant amount of silt and clay (the red stuff). Escaping water carries the red silts and clays away with it, leaving the white sand behind.

Three things to note. They can produce radial structure, they can produce fold-like structures, and they are pretty similar in size even though they are from different sandstones.

Now, for the record, I don't think that the radial structures in the 2.1 Ga structures are water escape features (I've another idea for them), I'm just showing that such structures can be formed inorganically. Although I am suggesting that water escape could be an explanation for the folding we see in the row 2 specimen.

The authors discount water escape as an explanation because the underlying sediment shows no disruption such as that shown in my Ediacaran example viewed from the side. Plus, shales are not known for their permeability (ability to allow water to flow through it). But we are dealing here with microbial mats. Mats can act as a barrier to water or gas flowing below them. In such instances, rapid loading by waning storm sediments could cause water or gas trapped under the microbial mats to tear through the mat, creating some neat folding patterns and not disturb the underlying sediment too much.

Actually I'd better show you some mats so that you know what I'm talking about. Here's one.

A juicy, yummy microbial mat, full of cyanobacterial goodness from Yellowstone Park. Photo Carnegie Institution

(And yes I do consider Yellowstone to be a good analogue for the 2.1 Ga Proterozoic, because while the hydrothermal pools are aggressive to microbial mat grazers, so was the 2.1 Ga Proterozoic, because, well, there weren't any.)

Do you think the microbial mat above looks like what the authors have imaged? I do.

And just so we're clear on how flexible microbial mats can be, here's another photo.

Photo from Cuadrado and Pazini (2007)

Here are some more Microbial mats.

Photo from Cuadrado and Pazini (2007)

Photo A shows microbial mats draped (folded) over cracks. Photo B shows gas bubbles trapped under a microbial mat. What? you thought I just made that gas stuff up?!

But this is the clincher for me.

Microbial mats at West Chaplin Lake (Bowman and Sachs 2008)

There are a number of things to notice here. Firstly the mats are not one continuous sheet, but here are two discrete mats about the same dimensions as the 2.1 Ga structures. Also note the lower mat has been torn to produce a clean, sharp, high angled edge. This shows that these things can be torn without losing structure, so simple folding should be no problem. Speaking of folding, check out the left margin of the upper mat. See the fold? Remind you of anything? This maybe?

So microbial mats can fold and wrinkle without tearing. I agree with the authors that the structures represent originally cohesive flexible sheets, but microbial mats not colonial multicellular organisms.

There are other methods to fold or wrinkle microbial mats. Storms could rip up mats or partially dislodge them for example, and the authors interpret the environment as deltaic, influenced by storms. Elephant skin textures on bedding plains have been interpreted as being caused by wrinkling and folding microbial mats.

I hope this has shown that the structures seen in the 2.1 Ga specimens, the folding and wrinkling, can be produced by inorganic means on biological sheets without invoking a new class of organism.

OK, on to numbers 4 and 5, the radial fabric.

This is one of the main arguments for the structures being a colonial multicellular colonial organism and it certainly is striking. but, as I showed above, radial fabrics can be caused by other things. inorganic things.

This irregular radial fabric, along with the the fact that it is commonly deflected to meet the edge of the structures is taken as evidence that the structures grew by peripheral accretion of flexible organic matter.

However, there are a few specimens where this radial fabric appears to go right through the structure.

Scale bar 1 cm

In one example, the fabric appear to actually cut through the central nodule

Scale bars 5 mm

How could a growth-related fabric cut through a nodule that wasn't there until late in the diagenetic process?

I think it's down to water again.

Lets assume that the mats/colonial organisms have gone through initial diagenesis and have been converted to pyrite. As diagenesis proceeds and load on the sediment column increase, the mudstones start to compact. Muds can contain 60% water which means that they have a long way to compact. Problem. Pyrite sheets can't compact.

I think that as compaction progressed and the pressure increased, the thin outer margin split in a regular pattern. As the process continued, the cracks spread further into the body of the specimens and sediment would be forced into the cracks. As we have an example of crack through the central nodule, it may be that this cracking occurred late in the diagenetic process, when compaction was reaching it greatest extent.

So rather than be evidence of peripheral growth, the fabric may be diagenetic.

Number 6 and 7 are linked, 6 is the carbon isotope ratio, and 7 the presence of steranes.

The authors found a difference in the organic carbon isotopic composition between the host rock and the structures. This, they say, shows that the structures were distinct organisms.

Without going into too much detail, carbon is present in two main isotopes 12C and 13C with one extra neutron in the nucleus. Organisms preferentially take up 12C in different amounts depending on their metabolic pathways, causing a shift in the 12C/13C ratio. Measuring this difference or delta 13C can help identify the origin of the organic mater.

The host rock has a delta 13C value of -27 while the structures had a value of -32. Now -27 is roughly an average value for eukaryotes, and so would be expected to represent the fallout from the water column into the sediment of dead eukaryote plankton. A value of -32 is more like bacterial signature. This would tend to support my suggestion that these structures are pyritised microbial mat fragments.

Number 7 is the observation that steranes have been found in the shales (note the shales not the structures). Steranes are compounds associated with eukaryotes. But if the explanation for the delta 13C values is correct, the steranes would also be produced from the eukaryote plankton and can't be used to support the suggestion that the structures are eukaryotes.

Finally number 8, a lack of support for any other inorganic origin.

I think I've put up enough suggestions for inorganic input into the formation of these structures. but here is a rough explanation:

- Microbial mats grow on delta front muds - probably as individual round patches, possibly connected by thin connections to other mats.

- Storm activity rips up or distorts the mats into folds and waning storm currents deposit a layer of sediment over them.

- Pore fluids equilibriate and the mats are surrounded by sulphide dominated pore fluids.

- Pyrite replaces the mats.

- As the basin fills and the sediment column increases, the muds compact. The distortion and pressure casuse the pyrite structures to deform slightly and crack around the margins.

- As pressure and compaction increase the cracks propagate and second pyrite phase occurs in the central area of some structures. It may be that the cracks allow pore fluid and organic-rich sediment into the centre of the structure allowing the second pyrite phase to occur.

I'd like to commend the authors for taking a multidisciplined approach to this work. It's an approach which I believe should be done more often, and will be more widespread in the future.

I'd also like to commend them for their use of new techniques and I hope they will continue to use them to explore more of the geological record.

Sorry that this post has been a bit of a smorgasbord, but my aim is to present a number of possible scenarios for the formation of these structures that do not require that they be large, multicellular, colonial organisms. There are other, unfortunately more mundane, explanations.

UPDATE 1

UPDATE 2

Albani, A., Bengtson, S., Canfield, D., Bekker, A., Macchiarelli, R., Mazurier, A., Hammarlund, E., Boulvais, P., Dupuy, J., Fontaine, C., Fürsich, F., Gauthier-Lafaye, F., Janvier, P., Javaux, E., Ossa, F., Pierson-Wickmann, A., Riboulleau, A., Sardini, P., Vachard, D., Whitehouse, M., & Meunier, A. (2010). Large colonial organisms with coordinated growth in oxygenated environments 2.1 Gyr ago Nature, 466 (7302), 100-104 DOI: 10.1038/nature09166

Diana G. Cuadrado and Natalia V. Pizani. (2007) Identification of microbially induced sedimentary structures over a tidal flat. Latin American Journal of Sedimentology and Basin Analysis. v.14 n.2 La Plata ago./dic. 2007

Jeff S Bowman and Julian P Sachs (2008) Chemical and physical properties of some saline lakes in Alberta and Saskatchewan. Saline Systems, 4:3 DOI: 10.1186/1746-1448-4-3

Catholic Church Angry at not Getting Special Treatment

2010-06-27T11:59:00.004+10:00

Cardinal Tarcisio Bertone, the Vatican Secretary of State, is annoyed.

Belgian authorities have seized around 500 files, searched church property, and held priests for questioning, over allegations of child sex abuse committed by a certain number of Church figures. The Belgian Catholic Church has previously apologised for it's silence on past sex abuse.

Cardinal Tarcisio Bertone, doesn't like it. He has called the detention of priests "serious and unbelievable". He said that "there are no precedents, not even under the old communist regimes".

He's right, there is no precedent for the church to be subject to the rule of law.

Cardinal Bertone also complained that bishops were kept in church during a search of church premises.

The Catholic Church not given special treatment? Shocking!

What Does a GOP Apology Cost

2010-06-26T15:19:00.003+10:00

By now everyone has heard of Joe Barton, ranking republican on the Congressional Committee on Energy and Commerce and his apology to BP.

However this allows us to calculate a handy base line.

Barton has received a total of $1,447,880 from oil and gas companies, and his apology consisted of 326 words.

The price of an apology from the ranking Republican on a Congressional Committee = $4440.00 per word.

Palaeoporn 15

2010-06-12T15:20:00.009+10:00

You spin my head right round, right round, . . .

Carrying on the theme of Palaeoporn 14, namely moulting in trilobites, here’s one to make your head spin.

Literally!

The trilobite at the top of the post is a big Redlichia takooensis (around 12-14 cm in length), common in the Lower Cambrian Emu Bay Shale, except that it's head is on backwards and inside out!

First a little background. The trilobite exoskeleton is rigid, and so to grow they need to shed this outer covering, expand, and mineralize another exoskeleton around the expanded body (crabs do this today, with soft crabs – those that have shed their exoskeleton and are awaiting the new exoskeleton to harden - prized as bait.)

Since the exoskeleton is rigid, there needs to be an exit strategy so that the body can get out of the old exoskeleton. This is usually achieved in trilobites by having lines of weakness – or sutures – at strategic places on the body, which preferentially break. These are usually placed on the head and around the eyes, and separate the central part of the head - or fixigena - from the outer part of the head - or librigena - which is also called the free cheeks 'cos they represent the cheeks of the head and they get freed up during moulting.

When the trilobite starts moulting, usually the suture lines break, the exoskeleton around the head separates into fragments (fixigena and librigena), allowing the body to exit through the head, leaving the exoskeleton intact, and the head fragments to fall back into place.

Usually.

Sometimes it doesn’t go to plan.

The free cheeks can be displaced, but that is usually the trilobite being careless on the way out. But sometimes things go wrong.

For comparison here is a proper R. takooensis (right, trilobite length 5 cm without spine) with its head on straight, fixigena and librigena all facing front and orientated correctly, even if the free cheeks are slightly displaced indicating that it is a moult.

So what happened to our backward friend up front?

Well, I'm pretty sure it wasn't born that way (no offense Jake), so it looks like a moulting accident.

Also the librigena isn't.

Liberated that is.

Although we don't have the whole body, the portion of the head outside of the eye (the librigena) is still in place indicating that the suture did not split.

What probably happened was that once the facial sutures failed to split, the exoskeleton broke behind the head. The animal then exited the old exoskeleton, pushing the head exoskeleton into the vertical and then beyond, which forced the head exoskeleton upside down and the front margin to point backwards.

In other words, imagine the head is an upside down bowl as in the diagram below, where F = front of the head, and B = back of the head.

Instead of splitting along the sutures, the whole head exoskeleton comes detached from the body exoskeleton. The trilobite then pushes its way out by forcing the head exoskeleton to tip 90 degrees onto the front margin, and then 180 degrees to lie upside down, with the front margin now pointing backwards and exposing the internal surface of the head exoskeleton.

The trilobite then escapes the old exoskeleton and is free to go.

Scary stuff perhaps, but not the worst example.

Next time - "Ultimate Moulting - when moulting REALLY goes bad"

Disco Tute Sows. Reaps.

2010-06-07T09:39:00.004+10:00

Looks like someone has had enough of the Disco 'tute's butchering of the truth.

The problem for the Disco 'tute is that Steve Matheson not only knows the science, but also is a Christian (not so easy to claim he's an atheistic materialist).

Having had a run in with the Disco 'tute's Steve Meyer and having been beaten around the head and face by what can only be described as a completely-out-of-his-depth Richard Sternberg wealding a feather pillow (see also here and here), Steve Matheson has declared open season on the Disco 'tute.

In a letter to Steven Meyer, Matheson writes in part:

. . . I can't state this strongly enough: the Discovery Institute is a dangerous cancer on the Christian intellect, both because of its unyielding commitment to dishonesty and because of its creepy mission to undermine science itself. I'd like to see you do better, but I have no such hope for your institute. It needs to be destroyed, and I will do what I can to bring that about.

Ouch!

This should be interesting.

Read Steve's account of the discussion of Steve Meyer's book Signature of the Cell at Biola University part I, part II, and part III.

Squid Wannabes in the Cambrian

2010-06-03T17:35:00.018+10:00

Another problematic Cambrian form finds a home. Once more the Burgess Shale comes up trumps, with the work of Martin Smith and Jean-Bernard Caron from the University of Toronto/Royal Ontario Museum shedding new light on Cambrian critters and the evolutionary things they get up to.

Ok. This is neat, and a group that occurs in the Burgess Shale, the Emu Bay Shale, and Chengjiang. The Burgess Shale form Nectocaris pteryx, and the closely related forms Vetustovermis from the Lower Cambrian Emu Bay Shale,

and the now not-synonymous Petalilium from the Lower Cambrian Chengjiang fauna, has been re-interpreted as a stem group cephalopod.

The arguments in favour of the forms being stem group cephalopods is persuasive (stem group forms lack one or more features characteristic of the last common ancester of the crown group).

The forms have a number of characters that link them with molluscs, and closely with cephalopods. These include the presence of tentacles - albeit only one pair, an axial cavity containing gills (possibly homologous with the mantle cavity of crown group cephalopods), and a funnel

They are also rare – ninety-odd specimens from the Burgess Shale may seem a lot, but it isn’t really. The Emu Bay Shale form Vetustovermis is very rare. I didn’t find one decent specimen when I worked on the deposit. But rare is good if you are trying to push the mollusc line, because molluscs don’t moult. Arthropods do. And moulds can fossilise. In effect, this is like leaving numerous photocopies of yourself in the fossil record. One arthropod can leave numerous fossils behind. Molluscs can’t. So we would expect them to be rarer than arthropods, as is the case here.

The eyes are interesting. They are preserved differently that other eyes in the Burgess Shale. Usually, eyes are preserved as a carbon film coated by clay minerals. This is similar to body preservation and is taken to indicate that the eyes were compound (made of calcite crystals) and thus robust enough to preserve the same way as the body. In Nectocaris (as in the similar Chengjiang form Petalilium) the eyes are preserved as a carbon film that covers a thick layer of muscovite crystals. This is interpreted by the authors as indicating that the eyes were hollow in life, similar to cephalopod (and our) eyes today, rather than the compound eyes of arthropods.

Another nice feature is the serial repeated pairs of gills. Modern cephalopods have one gill, or set of gills, but the sequence of repeated pairs of gills in Nectocaris (and in Petalilium, and Vetustovermis) is exposing its common ancestry with segmented forms. In other words the common ancester of molluscs and arthropods was a metamerically segmented form (a form with a series of similar segments, like a trilobite or worm). Nectocaris, with its sequence of repeated pairs of gills, is therefore, a neat intermediary between the metamerically segmented ancestral form and the derived, more modern forms that have lost the segmentation. In mean, if you'd have asked a palaeontologist what a stem group cephalopod would look like, the answer would have been paired gills all the way down!

This group appears to lack a horny beak, a radula, a shell, and at least eight tentacles, which is why they are considered stem group forms. The last common ancester of the cephalopods is considered to have had all of these.

I have a few issues however.

First, have to say I’m not a fan of the paper’s title, Primative soft-bodied cephalopods from the Cambrian. “Primitive”! Oh dear, I had though we had stopped using that term – Early perhaps). And they are not strictly cephalopods (they are however, Conchifera). So, "Early Conchiferids from the Cambrian" perhaps (a bit dry I’d admit), or my personal choice, "Squid wannabes from the Cambrian".

Second, I am not a fan of the reconstruction either. Not the drawing itself – I’m a big fan of Marianne Collins’ work – but of the way it hovers with the funnel aimed downward like a Harrier Jump Jet or, as in Nature News and Views, the rocket underneath the Space Shuttle. Ugh!

It’s very unlikely that the funnel would have been used like that. One of the specimens has it in that position (figure “f” in first image) but it is unlikely to represent the life position. Burgess Shale fossils are found in all orientations, and numerous other specimens of Nectocaris have the funnel in various orientations. I think that figure “f” has a bad case of flacid funnel, probably post mortem.

The funnel was probably used to move forwards and backwards, but also maybe to blow fine sediment away from shallowly buried prey, or even blow them so that they tumbled which disorientated them, make them easier to catch. But what prey did they hunt? This is especially interesting given the jaws, or rather the lack of them! Which brings us to . . .

Third, where’s the jaws? It looks like they are absent in Nectocaris. This is strange, as the presence of teeth or radulas are well established in the Mollusca by the Middle Cambrian Burgess Shale time. Modern cephalapods have a beak, but the radula is reduced in octopus, and is absent (or extremely reduced) in Spirula, the Ram’s Horn Squid.

The authors say that the absence could be due to it not being preserved or that it is too small to preserve. I’m not buying that it didn’t preserve. Hard parts of other organisms preserve just fine in the Burgess Shale. But it could be that they were very small. Spirula is a small (around 4 cm) deep water squid that either has a very small or non-existant radula. Spirula feeds on plankton, so it could be that Nectocaris also fed on tiny plankton as well.

There is some vague feature which the authors claim could be mouth parts. If so it would suggest a diet of soft bodies organisms or very small organisms such as plankton.

So three Cambrian forms tidied up quite nicely, and a neat transitional form (gasp!) as well! Cambrian squid wannabes with a hangover from their metamerically segmented ancestry.

Smith, M., & Caron, J. (2010). Primitive soft-bodied cephalopods from the Cambrian Nature, 465 (7297), 469-472 DOI: 10.1038/nature09068

Smith, M., & Caron, J. (2010a). Primitive soft-bodied cephalopods from the Cambrian: Supplimentary Information Nature, 465 (7297), 469-472 DOI: 10.1038/nature09068

Chen, Jun-yuan; Huang, Di-ying; Bottjer, David J. (2005). "An Early Cambrian problematic fossil: Vetustovermis and its possible affinities.". Proceedings of the Royal Society, Part B 272 (1576): 2003–2007. doi:10.1098/rspb.2005.3159.

Cambrian Critters in the Ordovician 2

2010-05-30T16:35:00.016+10:00

During the 46-million-year Ordovician Period (489–443 mya), a phenomenal array of adaptive radiations of "Paleozoic- and Modern-type" biotas appeared in marine habitats, the first animals walked on land, and the plants appeared.

This Great Ordovician Biodiversification Event represents a tripling of diversity at the family level, and a quadrupling at the genus level, from those in the Cambrian.

The number of families reached by the end of the Ordovician remained fairly constant (except for a number of mass extinction events) for almost 200 million years. Articulate brachiopods, conodonts, graptolites molluscs, crinoids, and trilobite groups all became established of diversified greatly during this time.

A major question is what happened to the Cambrian faunas - as typified by the Burgess Shale, the 'soft-bodied', or poorly mineralised, organisms that are found in numerous Cambrian deposits. They are by-and-large absent from the Ordovician.

We do have a large number of Cambrian sites with exceptional preservation (the Bugress Shale being the ‘type’ example), but from the Ordovician, not so much. In fact very few. In fact, bugger all!

What Ordovician exceptional preservation we have comes from the middle and late Ordovician, the Beecher’s Trilobite Bed, New York, the Soom Shale, South Africa, Winneshiek, Iowa, and a couple of localities in Manitoba, Canada.

All localities represent restricted faunas from extreme environments (low oxygen) and not examples of more diverse, open marine environments. (Yes, the Burgess Shale may well represent a low oxygen environment, but the biota it contains represents a diverse open marine environment.)

No examples of exceptional preservation have been found from the early Ordovician.

Given this extreme lack of exceptional preservation, our understanding of this great biodiversification event is almost entirely based on the shelly fossil record. What we get, is a spectacular rise in the shelly fossil record.

This leads to the obvious question. What happened to the Cambrian critters?

There are two main theories to explain that wholescale change in faunas. One is that the Cambrian forms were replaced by Ordovician forms. The other is that the exceptional preservation we see in Cambrian deposits simply does not occur in the Ordovician, and so the missing forms are due to a taphanomic, or preservational, bias. So which is it? replacement of preservational?

Introducing the Fezouata biota from the lower Ordovician of Morocco.

This represents the first site of exceptional preservation from the lower Ordovician, and (if that wasn’t important enough) the first from a ‘normal’ open marine environment.

Over 50 different taxa have been collected so far indicating an open marine, deep water assemblage that has been trapped beneath, or brought in by, storm deposits. Limited bioturbation indicates low oxygen which would account for the exceptional preservation. The fauna is a mix of typical Ordovician forms and typical Cambrian Burgess Shale-types, although there are similarities with the Chengjiang fauna from China, both in terms of fossils and depositional environment.

One cool find is a xiphosurid (a horseshoe crab - everyone's favourite chelicerate). The horseshoe crab fossils are the oldest yet found, suggesting that their roots may dip into the Cambrian. What is really cool is that one of the two species of horseshoe crab has a fully segmented opisthosoma (it is either partially or fully fused in other forms), suggesting evolution from a segmented ancester. The other has a fully fused preabdomen (quite a derived feature) and is similar to existing forms (though not the same.)

This has major implications for the transition from Cambrian fauna to the Palaeozoic fauna represented by Ordovician forms. Namely that the Cambrian critters hung on for a considerable time after the end of the Cambrian and intermingled with Ordovician forms. So there was no wholesale replacement at the end of the Cambrian. Both sets mixed.

However it is interesting to note that this deep water deposit was close to the South Pole during lower Ordovician times. The deposits represent a deep, cold water environment. Cambrian deposits with exceptional preservation, by contrast, were primarily from low latitudes, near the paleoequator, and from shallow water.

It may be that the Fezouata biota represents a refuge for the Cambrian forms - much like modern brachiopods are excluded from tropical areas and are mainly found in temperate and cold deep water today.

So this biota shows that Cambrian forms persisted well into the Ordovician, but a shallow water site of exceptional preservation is needed to see if the Cambrian critters were mixing it with the Ordovician upstarts, or were just hanging on along the margins.

Thanks to Paul H.

Van Roy, P., Orr, P., Botting, J., Muir, L., Vinther, J., Lefebvre, B., Hariri, K., & Briggs, D. (2010). Ordovician faunas of Burgess Shale type Nature, 465 (7295), 215-218 DOI: 10.1038/nature09038

Cambrian Critters in the Ordovician

2010-05-15T15:27:00.003+10:00

There's a paper in Nature on a new Ordovician site with a range of critters resembling Cambrian fossils.

I am waiting to get my hands on a copy of the paper to comment, but until then Brian Switek has it covered here.

One thing though. The deposit is apparently from deep water. This may well be an example of critters being forced out of the near shore by competition and hanging on in a deep water 'refuge'.

More once I get the paper.

Palaeoporn 14

2010-04-26T14:29:00.008+10:00

Ménage à trois!
These are Estangia bilobata trilobites from the Lower Cambrian Emu Bay Shale on Kangaroo Island, South Australia. Estangia is the most common fossil found in the Emu Bay Shale. However, these came from the outcrop of Emu Bay Shale at Emu Bay, and not from the more famous site further along the coast that contains exceptionally preserved fossils such as Anomalocaris and Myoscolex. (The Emu Bay Shale outcrops at two locations on Kangaroo Island)

These little critters show the difference between the two depositional sites. The site with exceptional preservation shows evidence - palaeontological (whole specimens, low diversity) sedimentological (fine grained sediments), and chemical (evidence of reducing environment-enriched trace elements) - of a low energy, low oxygen environment conducive to exceptional preservation.

On the other hand at Emu Bay the site shows evidence of a higher energy, higher oxygen depositional environment. This is because the sediments show more interbedded sands and silts (coarser grained therefore higher energy), oxidating environment-enriched trace elements, and the fossils do not show exceptional preservation, and are fragmented.

In the example above, the fossils assemblage comprises the heads of three Estangia trilobites (the lower one is both turned over and spun through 180 degrees). The heads are not complete. The sides of the head - the librigena (or the free cheeks) are missing. This shows that the heads represent molts.

Trilobites are arthropods and so have to molt the outer exoskeleton in order to grow. To do this, they have special lines of weakness in the exoskeleton called sutures. When the trilobite molts, these suture lines break apart, allowing the trilobite to leave the exoskeleton. These sutures are particularly obvious on the head where they run from the margin down to the eye, around the eye and then back out to either the side margin or the back margin.

In this case the suture lines are opisthoparian,
as they run from the eye to the back of the head rather than out to the side They run along the eye so that the eyes will be the first thing to break out of the old exoskeleton - allowing the trilobite to keep its vision while the molting process continues. This results in the librigena breaking away from the head. Often the molting process breaks the attachment between the head and the rest of the body, resulting in the head becoming detached from the rest of the body.

Since these fossils comprise the cranidium only (head minus the librigena), this indicates that they are molts and that they have been sorted by currents that have separated them from the body and librigena.

Compare this with another Emu Bay Shale Estangia, this time from the site of exceptional preservation (right).

Here the head and body is present. However, it is still a molt because the librigena have been freed from the head. In this specimen, the right librigena (outlined) is still associated with the body but has moved some distance away, and is both turned over and spun through 180 degrees so the the spine (that normally points backwards) now points forwards.

So the three in the top image represent a disarticulated random grouping, and have not been caught in flagrante delicto. So move along . . . nothing to see here . ..

Diagram credit:
Trilobite Facial Sutures

Possible Association Between Multivitamins and Breast Cancer

2010-04-18T13:49:00.003+10:00

It's well known that the primary result of taking vitamins is basically expensive urine (e.g. here), despite alternative medicine sites claiming it's a myth.

However, now there may potentially be a much more serious downside to multivitamins than just expensive urine - breast cancer.

A study published in the American Journal of Clinical Nutrition studied 35,000 women over a 10-year period.

In 1997, 35,329 cancer-free women completed a self-administered questionnaire that provided information on multivitamin use as well as other breast cancer risk factors.

During a follow-up, 974 women were diagnosed with incident breast cancer. When researchers checked, they found that women using multivitamins were over-represented. For those taking at least seven vitamin pills per week, the risk of contracting breast cancer increased by 19 percent in comparison with those who did not take vitamins at all.

The study concluded that the results suggest multivitamin use is associated with an increased risk of breast cancer, and that this observed association is of concern and merits further investigation.

It is known that some women who use multivitamins get firmer breasts than other women, through an increase in breast tissue density, and significant increases the density of breast tissue is a strong risk factor for breast cancer.

This is not a causal link, but, as the study concludes, needs further investigation.

Complimentary health is a A$2.5 billion industry in Australia.

Multivitamin use and breast cancer incidence in a prospective cohort of Swedish women. Susanna C Larsson, Agneta Åkesson, Leif Bergkvist and Alicja Wol. American Journal of Clinical Nutrition, March 24, 2010. doi:10.3945/ajcn.2009.288

Helpful Hints when Protecting Pedophiles

2010-04-10T13:16:00.004+10:00

Don't leave a paper trail.
The ongoing PR disaster that is the current revelations about the pedophile priests cover up by the Catholic Church has now drawn Ratzinger even more into the frame.

The BBC is reporting on a letter delaying action on a priest in America in 1985, and signed by then Cardinal Ratzinger. The first evidence of direct involvement by Ratzinger.

According to the BBC, in 1978 a catholic priest Stephen Kiesle was sentenced to three years of probation for lewd conduct with two young boys in San Francisco. The Oakland diocese had recommended Kiesle's removal in 1981 but that that did not happen until 1987.

Cardinal Ratzinger took over the Congregation for the Doctrine of the Faith, which deals with sex abuse cases, in 1981.

So the diocese asked for the Kiesle to be defrocked in 1981. In 1985 Ratzinger wrote to the diocese:

Most Excellent Bishop

Having received your letter of September 13 of this year, regarding the matter of the removal from all priestly burdens pertaining to Rev Stephen Miller Kiesle in your diocese, it is my duty to share with you the following:

This court, although it regards the arguments presented in favour of removal in this case to be of grave significance, nevertheless deems it necessary to consider the good of the Universal Church together with that of the petitioner, and it is also unable to make light of the detriment that granting the dispensation can provoke with the community of Christ's faithful, particularly regarding the young age of the petitioner.

It is necessary for this Congregation to submit incidents of this sort to very careful consideration, which necessitates a longer period of time.

In the meantime your Excellency must not fail to provide the petitioner with as much paternal care as possible and in addition to explain to same the rationale of this court, which is accustomed to proceed keeping the common good especially before its eyes.

Let me take this occasion to convey sentiments of the highest regard always to you.

Your most Reverend Excellency

Joseph Cardinal Ratzinger

So . . , like . . , 'we think the arguments are grave, but we need more time, think about how the Church would look if we defrocked him, consider the impact on him, and be sure to minister to him'.

Nothing about protecting the flock that placed their trust in the Church and who may be in harms way.

Now the Church claims that this must be taken in context of a long series of correspondence on this matter between the Vatican and the diocese, and this is true. There may be other letters laying out protections for the flock, but if there are, surely the Vatican could release them?

Catholic Sycophancy 101

2010-04-05T11:25:00.004+10:00

The latest PR disaster that is the Catholic church continues unabated. And much of it has to be put at the feet of Ratzinger. Confirming once again what a terrible "choice" he was. I put choice in inverted commas because, of course it was no such thing.

Having run the Vatican for several years while the incumbent Pope was literally a dribbling idiot, he successfully entrenched the fundamentalists in power behind the scenes. Having done so, the majority had unelectable sycophants, while all the best candidates were moderate and so blocked by Ratzinger's faction. Having created the impasse Ratzinger graciously steps up to the plate for the good of the Church - his church of course.

The problem with surrounding yourself with sycophants is that, well, their qualifications are that they are sycophants, not that they have experience or expertise with the issues.

This has been highlighted by the series of PR disasters the Vatican continues to stumble through.

The welcoming back into the Church of a holocaust denier.
The excommunication of people involved with saving the life of a 12 year old rape victim.
The ongoing falsehoods regarding condoms and AIDS in Africa.

Now comes the latest scandels, the continuing revelations of pedophilia by Catholic priests and the failure by the church to deal with it.

This time Ratzinger is intimately involved, as it appears he was informed about these activities but failed the victims. In fact, he apparently issued an letter in 2001 instructing that all case should be kept quiet and dealt with within the church (now I'm no lawyer, but isn't instructing someone to hide a crime, itself a crime?)

Clearly the Catholic church holds it's priests to a different standard to everyone else. That standard appears to be 'all priests are considered innocent until the crime becomes public'.

The latest attempts at damage control continues the inept performance of this Pope and the Vatican.

The victims have been blamed.
The media has been blamed.
The holocaust has been invoked to support the church.
The 'the fact that some boys were pubescent means that it wasn't pedophilia' defence. (No, seriously!).

The latest defence - change the story. It's now all about atheism

And with that we welcome the latest sycophant to be promoted - Bishop Anthony Fisher OP, DD, BA(Hons), LLB, BTheol(Hons), DPhil, the new Bishop of Parramatta, and historical ignoramus.

In his first easter message The good Bishop says:

Last century we tried godlessness on a grand scale and the effects were devastating. Nazism, Stalinism, Pol-Pottery, mass murder, abortion and broken relationships: all promoted by state-imposed atheism or culture-insinuated secularism, the illusion that we can build a better life without God.

Natzism? Really? The army that had "Gott Mit Uns" on their uniform was godless?

The new Bishop of Parramatta, on message and clueless - should go far in Ratzinger's brave new world.

New Ediacaran Trace Fossils

2010-03-08T15:55:00.019+11:00

A paper in Geology has just reported a new type of trace fossils from the Ediacaran of Mistaken Point, Newfoundland.

This is interesting because until now trace fossil diversity in the Ediacaran has been very limited, with only three recognised traces fossil types:

1) Helminthoidichnites
The most common from, composed of simple groove traces with levees. Probably formed in the topmost 10mm of the sediment. They are commonly preserved as negative epireliefs or negative hyporeliefs, indented into the bottom of the overlying beds. Sediment is commonly displaced to form marginal raised ridges. There were probable tubes indicating organisms that may have been round. Some directional meandering is evident.

2)Radulichnus
A form with fine ridges, arranged in fans and associated with Kimberella in a few instances. Broadly analogous to mollusc radula-like grazing. Kimberella occurs at the apex of the fans and appears to have scraped bio-material from the sediment with a proboscis.

3) Resting traces, particularly Dickinsonia
Evidence of serial mat "feeding" dissolution by creeping mat-like animals. These are outlines of organisms that have been impressed into algal mats covering the sediment, often in association with similar-sized body fossils. These are often found as positive epirelief - sticking out from the under side of the bed, as apposed to normal Dickinsonia body fossils which are found as negative epirelief - an indentation into the bottom of the bed.

The latest finds from Newfoundland have been found on the top of green mudstone overlain by a volcanic tuff which has protected the traces. If should be noted that the preservation at Mistaken point differs from most Ediacaran sites in that the fossils are preserved on the top of beds, under a volcanic tuff which blanketed the forms when alive and protected them. Most Ediacaran fossils occur on the base of coarse sandstone beds which smothered the organisms (see An Introduction to the Ediacaran Fauna).

Over 70 straight traces, ranging from 1.5 to 17.2 cm in length and up to 13 mm in width have been found. The surfaces of the traces are marked by regular crescentic internal divisions, formed by thin ridges of siltstone with a spacing of approx. 1 mm.
Locomotion trace from Mistaken Point Formation, Newfoundland.
A) Largest observed trail on bedding plane. B–D are
close-up images of crescentic internal divisions in A. B) Distal end of
trail. Note pyrite crystals embedded in ash surrounding trail. C) Central
section of trail. D: Proximal section of trail with terminal circular
impression. Scale bars = 1 cm.
Each trace typically bears marginal ridges which the authors claim provides key evidence for movement of an object along the surface of the sediment, and can be used to distinguish trace fossils from abiogenic structures. At the far end of several specimens, a negative circular impression can also be seen, which the authors interpret as the mould of the trace maker itself.

The largest trace on the trace-bearing bedding plane, Mistaken Point Formation, Mistaken Point Ecological Reserve, Newfoundland, Canada. Note the clear terminal disc (at right), prominent marginal levees indicating displacement of sediment, and the positive internal crescentic ridges.

The authors interpret the trace as being made by a cnidarian-like organisms similar to Urticina, a modern sea anemone.

Modern actinian (Urticina) trails in mud, produced in our
marine aquaria. Note concave-forward hemispherical structures
(at left) and positive marginal ridges (right).
Scale bar = 3 cm.
This is a big claim - that a cnidarian-grade organism was crawling around the Ediacaran. Of course a number of people have been claiming that this level of organisation was around then, but this would be an important step in supporting evidence.

There are a few issues however.

These traces are extremely rare, and are not found in other locations. An explanation for that is the differing preservatonal styles, but even so, some similar finds would be expected. Also a number of finds of tube-like remains have been found along with the 'stitch and groove' pattern shown by the Mistaken Point forms, and have been interporeted as body fossils. So there is still some uncertainty here. Of course, finding a sea-anemone-like form at the end of one of these trails would be nice, but there is still a lot we need to understand about stitch and groove forms before we can say with any degree of certainty that these forms were made by cnidarian-grade organisms

Images
Helminthoidichnites: http://en.wikipedia.org/wiki/Ediacara_biota
Dickinsonia trace: www.evolbiol.ru/fedonkin_metazoa.htm

Liu, A., Mcllroy, D., & Brasier, M. (2010). First evidence for locomotion in the Ediacara biota from the 565 Ma Mistaken Point Formation, Newfoundland Geology, 38 (2), 123-126 DOI: 10.1130/G30368.1

Deltoid in the Top Thirty

2010-02-10T22:57:00.004+11:00

Our very own Deltoid has made it onto a list of the top thirty science blogs at the Times Online.

Polite applause.

Unfortunately, the Times cannot resist a nod to its climate-denialist stance and has included the truly woeful climate-denialist blog Watts Up With That.

The comments make for interesting reading (and I agree with some of them that Times Online should replace Watts Up With that with Bad Science.)

Creationists Lose Again

2010-01-13T23:02:00.005+11:00

In 2005 the Association of Christian Schools International (ACSI) sued the University of California who had decided that their school qualifications were unsuitable as entry qualifications. This was due in part, to the use of creationist-leaning biology textbooks published by Bob Jones University Press and A Beka Books (including Biology: God's Living Creation and and Biology for Christian Schools.

Michael Behe was an expert witness for the ACSI, with Donald Kennedy and Francisco J. Ayala expert witnesses for UC.

The trial judge granted the defendants' motion for summary judgment, and the ACSI appealed.

The Appeals Court affirmed the trial court's ruling that the University of California's policy was constitutional.

Money quote

"The plaintiffs have not alleged facts showing any risk that UC's policy will lead to the suppression of speech. ... the plaintiffs fail to allege facts showing that this policy is discriminatory in any way. ... The district court correctly determined that UC's rejections of the Calvary [Baptist School] courses [including a biology class that used Biology: God's Living Creation] were reasonable and did not constitute viewpoint discrimination. ... The plaintiffs assert a myriad of legal arguments attacking the district court's decision, all of which lack merit."

So no change there then.

Another victory against creationism, but as Larry Moran keeps saying, the fact that these battles are being undertaken in court is a failure, despite the fact that we keep winning.

Also this is the second time Michael Behe has been an expert witness for the loosing side.

More on this from the NCSE

Palianation

2010-01-12T22:07:00.001+11:00

Sarah Palin joins Fox News.

Like noone saw that coming!

Why Dinosaurs Hate Christmas

2009-12-24T21:50:00.001+11:00

Back by popular demand.

Did you know that most dinosaurs hate Christmas? It’s true, they do. And it’s not because they couldn’t get a handle on the present wrapping (or unwrapping for that matter) either. No, there is a very good reason why Dinosaurs hate Christmas.

However, before explaining why dinosaurs hate Christmas, lets deal with some startling new information. Everyone is familiar with the standard explanation for the extinction of the dinosaurs. I've included a common representation of the event.

However, startling 'evidence' has been presented which suggests another reason for what happened. The evidence is still officially hidden by the authorities, but one startling image has been smuggled out and is shown here for the first time.

It is claimed that it was an early experiment on propulsion systems that went wrong and had to be ejected. Shocking as this image is, there are some who claim that it is a forgery and just another shot by those at war with Christmas.

However, this is not the reason that dinosaurs hate Christmas. To understand that we need to know what dinosaurs are.

In his classic 1842 publication on dinosaurs, Richard Owen named and defined the Dinosauria as:
a group of exceedingly large, pachydermous reptiles from the Second Age . . . includes Megalosaurus, Iguanodon and Hylaeosaurus.

In 1997, Tom Holtz provided a different definition:
the last common ancester of Megalosaurus andIguanodon and all its descendants.
If it's changed since then, blame Holtz, but any changes will be mainly deckchair shuffling on the SS Chicxulub.

Anyhow, the thing about this definition is that, nestled between the Megalosaurs and the Iguanadons, are the Dromaeosaurs, and directly related to the Dromaeosaurs, and so one of the descendants mentioned above, is a little group called Aves!

So with the mass slaughter of ~~birds~~ dinosaurs every Christmas, wouldn't you hate Christmas?

If you insist in participating in this slaughter, at least make sure you cook your dinosaur correctly:

1. If your dinosaur is frozen, fully thaw it.

2. Don’t stuff the dinosaur. By the time the stuffing reaches a safe temperature, the meat is overcooked.

3. Cover the dinosaur breasts with ice while the rest of the dinosaur warms to room temperature. Don’t leave the dinosaur out for more than 3 hours. At this point, the breast will be about 4 centigrade (40^o Fahrenheit), while the rest of the meat will be at 16 centigrade (60^o Fahrenheit).

4. Put the dinosaur in the oven and cook according to your favorite recipe.

5. With a meat thermometer, check temperature. Take out of the oven when legs reach 82 centigrade (180^o Fahrenheit) and breast hits between 68 and 71 centigrade (155^o and 160^o Fahrenheit).

Ho Ho Bleedin' Ho.

Let It Snow, Let it Snow, Let it Snow.

2009-12-24T01:06:00.003+11:00

Snow at Christmas. Yay.

Well, snow just before Christmas anyway. And no, it's not snowing in Australia, I'm in London for Christmas and January.

Missed the Eurostar debacle by a few days, so snow and an uneventful trip from Paris to London by train. Things are looking good.

Chocs and wine at the ready, Saturnalia is go. Lo lo lo.

Livelife 3 - Tiliqua rugosa

2009-11-19T23:01:00.007+11:00

Dip and strike?! We don't need no stinkin' dip and strike!

This blue tongue lizard was clearly not fooled by the request to take a dip and strike on an outcrop of late Neoproterozoic cap carbonate in the Flinders Ranges. He was also clearly unimpressed with the fact that he was standing at the end of the 'Snowball Earth' and the start of the Ediacaran Period. There's just no pleasing some lizards!

The fat tail shows that he was in good condition as that's where they store their fat reserves.

Blue tongues, shinglebacks, or sleepy lizards, as they are commonly known, are members of the skink family (Scincidae).

The Cambrian Explosion, the Discovery Institute, and the Smithsonian

2009-10-10T13:48:00.008+11:00

I intend to write a set of blog posts addressing the comments and thoughts on Darwin’s Dilemma from people who have seen the film. This is useful because people who do not have a background in the Cambrian Explosion or palaeontology are the people that the Discovery Institute is hoping to mislead. So what such people are taking away from the film, the messages that the Discovery Institute is hoping to instill, the questions raised in people’s minds, etc., are worth addressing.

Previous posts: The Cambrian Explosion, the Discovery Institute, and
Charles Doolitte Walcott (part 2)
James Valentine
Prof Paul Chien
Cambrian Ediacaran Extiction
Cambrian Diversity
Charles Doolittle Walcott

The California Science Center in Los Angeles was scheduled to show Darwin's Dilemma of October 25th, but has just announced that it has cancelled the performance. The Discovery Institute is making the usual claim of censorship, and that the cancellation was due to the Smithsonian putting pressure on the California Science Center. The Smithsonian? Well yes, the Smithsonian. But to understand this you have to understand the Discovery Institutes tactics here.

This is all part of the Discovery Institute's desperate attempt for legitimacy through the tactic of 'legitimacy via association'.

This operates by having recognised scientists in you product (even if you have to mislead them into appearing, and they do not support the claims of intelligent design creationism), showing a product in a museum (Seattle) or other science venue, which, by association, validates the claim that the content is scientific.

In their latest attempt at 'legitimacy via association', the Discovery Institute issued a press release promoting Darwin's Dilemma being shown at the California Science Center in Los Angeles, by referring to the Center as the Smithsonian Institution's west coast affiliate. See the tactic?

'We are showing Darwin's Dilemma at the California Science Center which is THE SMITHSONIAN INSTITUTE'S WEST COAST AFFILIATE! SEE? SCIENCE CENTER! SMITHSONIAN! ARE WE LEGIT OR WHAT?!'

The problem for the Discovery Institute is that this particular dishonest tactic is easy to expose.

Firstly, the claim that the California Science Center is the Smithsonian Institution's west coast affiliate. Is it? Actually, while it is a west coast Affiliate, it isn't the west coast Affiliate. The Smithsonian is currently affiliated with 20 fine Californian institutions:

Aerospace Museum of California - McClellan
Agua Caliente Cultural Museum - Palm Springs
Arts Council for Long Beach - Long Beach
Blackhawk Museum - Danville
California Science Center - Los Angeles
Cerritos Library - Cerritos
Chabot Space and Science Center - Oakland
Discovery Science Center - Santa Ana
Fresno Metropolitan Museum of Art and Science - Fresno
Hiller Aviation Museum - San Carlos
Japanese American National Museum - Los Angeles
LA Plaza de Cultura y Artes - Los Angeles
Mexican Heritage Plaza - San Jose
Millard Sheets Center for the Arts at Fairplex - Pomona
Museum of Latin American Art - Long Beach
Riverside Arts and Cultural Affairs Division, Riverside Metropolitan Museum - Riverside
San Diego Air and Space Museum - San Diego
San Diego Natural History Museum - San Diego
Sonoma County Museum - Santa Rosa
Western Center for Archaeology and Paleontology - Hemet

But lets look further up the west coast, north to the State that flies on her own wings. Any Smithsonian Affiliates there? Well yes,

Evergreen Aviation and Space Museum - McMinnville

But wait there's more west coast to go. Up to the Evergreen State. Any Smithsonian affiliates there? (you know the answer, right?)

Whatcom Museum of History and Art - Bellingham
The Museum of Flight - Seattle
Wing Luke Asian Museum - Seattle
Northwest Museum of Arts and Culture - Spokane

Hang on. Say what? Two in Seattle?! Isn't the Discovery Institute headquartered in Seattle? They missed two Smithsonian Affiliates right there in their home town?! Oops.

All in all, 25 Smithsonian Affiliates on the west coast.

OK, that's exposes the falsehood of the claim that the California Science Center is the Smithsonian Affiliate on the west coast, but what about the affiliate link anyway, what does that mean?

Clearly the Discovery Institute would want you to think that Affiliates are the Smithsonian in the regions, but what is an Affiliate?

Smithsonian Affiliations offers broader opportunities than those found in standard museum loan programs. In addition to artifact loans, Smithsonian Affiliations helps member organizations identify appropriate resources within the Smithsonian to accompany exhibit loans: education and performing arts programs, expert speakers, teacher workshops, and technical assistance.

So Affiliates are entirely independent from the Smithsonian, and being an Affiliate simply means that they can gain access to the Smithsonian collections to support their own exhibitions. The Smithsonian has no control over the day to day operations of any Affiliate.

So, the California Science Centre is just one of 25 Smithsonian Affiliates on the west coast, and being an Affiliate simply means you get access to the Smithsonian collections, and the Smithsonian has no day to day control over Affiliates.

All this may appear to be nitpicking, but this slight of hand (or in this case slight of phrase) is the modus operandi of the Discovery Institute's dishonest tactic of 'legitimacy via association'.

Of course there would be no need of the tactic of 'legitimacy via association' if your claims weren't scientifically vacuous, but this is the Discovery Institute.

The Cambrian Explosion, the Discovery Institute, and Charles Doolittle Walcott (Part 2)

2009-10-05T18:24:00.004+11:00

Stephen Meyer:'Like Darwin, Walcott thought that the Cambrian explosion was an illusion. He was convinced that the fossils were there. They were just inaccessible to scientific discovery. And he expected that they would eventually be found someplace buried deep beneath the oceans.'

Wow, a correct summary by Stephen Meyer! Yes, Walcott thought that the Precambrian sediments with fossils would be found far out to sea for the reasons stated here. He named the period of non-deposition on the continents at this time the Lipalian.

Narration: 'For decades, Walcott’s hypothesis was widely accepted, but untestable. However, later in the 20th century, new technologies [ocean oil platform] led to empirical conclusions.'

Nice of Stephen Meyer and Paul Nelson to pass the lie to the narrator rather than tell it themselves.

No, Walcott’s idea was not widely accepted at the time, let alone for decades. It was quietly forgotten:

He [walcott] suggested that a widespread unconformity at the top of the Proterozoic represented an interval oftime, the Lipalian, in which such an earlier fauna developed elsewhere, but was not recorded in any outcrop. The concept of naming a gap to represent a major missing segment of geologic time, did not result in any comment from the geologic community and the Lipalian Interval vanished (Yochelson 2006)

In the meantime people were finding Precambrian fossils right here on land, oblivious to the fact that they were supposed to be looking for them way out to sea:

Glaessner, M (1959) Precambrian Coelenterata from Australia, Africa and England. Nature. 183. P.1472-1473.

Ford T.D. (1958) Precambrian fossils from Charnwood Forest. Proceedings of the Yorkshire Geological Society. 31. P.211-217.

Stephen Meyer: ‘Once the oil companies started to drill offshore, they brought up what are called drill cores, and inside the core were hunks of sedimentary rock, and some of those rocks contained fossils. But none of them were made by animals that lived before the Cambrian explosion.’

This is an attempt to pretend that geologists were hoping to find Precambrian fossils in drill core. But the idea is nonsense, since it had been known for a long time that there were no Precambrian rocks out to sea and besides, people do not as a general rule drill Precambrian rocks for oil. Almost all offshore oil wells bottom out well before any Precambrian rocks are reached, so we wouldn’t expect to see Precambrian rocks, let alone fossils.

Besides, oil drilling is too close inshore to be useful. Real deep sea drilling didn’t take place until the 1980s, with the the Joint Oceanographic Institutions for Deep Earth Sampling Ocean Drilling program.

Narration: ‘Since the 1960s, scientists have also used radioactive minerals and evidence of changes in the earth’s magnetic field to analyze and date undersea sediments. From extensive surveys they have created this digital map that defines the age of the sea floor.’

Correct, which is why geologists were not hanging out for drill core to find Precambrian fossils. They already knew that the sea floor was too young. The Discovery Institute can’t have it both ways – hanging out for drill core at the same time as knowing the sea floor was too young.

Stephen Meyer: ‘We now know that the oldest rocks on the bottom only date back to the Jurassic period, which means that on the standard geologic time scale, they’re hundreds of millions of years younger than the rocks below the Cambrian strata.’

"We now know"? "We NOW know"? Stephen, we knew 40 YEARS ago! Again, the Discovery Institute can’t have it both ways – hanging out for drill core at the same time as knowing the sea floor was too young.

Paul Nelson: ‘If you are looking for the ancestors to the Cambrian groups, the last place you would expect to find them is out somewhere on the sea floor. Those rocks are much too young.’

Well gee Paul, we’ve known that for 40 years, and have had Precambrian fossils on land for over 50 years, but thanks for pointing that out.

OK, it is clear now that the Discovery Institute is trying to lay the groundwork for Intelligent Design creationism by trying to paint geologists as holding onto Walcott’s Lipalian idea as the only hope to explain the lack of Precambrian fossils.

Their version of events does not tally with reality, but then this is the Discovery Institute.

Yochelson, E.L. (2006) The Lipalian interval: A forgotten, novel concept in the geologic column. Earth Science History. 26(2), p.251-269

The Cambrian Explosion, the Discovery Institute, and James Valentine

2009-10-05T12:06:00.007+11:00

Update

Professor Valentine has endorsed the use of his statement on this site.

24 September 2009

What James Valentine Really Thinks About Evolution
Dr. James Valentine, an evolutionary biologist and Professor Emeritus in the Department of Integrative Biology at the University of California at Berkeley, is featured in the intelligent design movie Darwin’s Dilemma.

I wish to clarify my role in the new film Darwin’s Dilemma. When I was interviewed about a decade ago for the material used in this movie, I was unaware that this interview might appear in a film promoting intelligent design. My appearance should not be misconstrued as support for any creationist agenda.

I support evolution.

I disagree with the view that the best explanation for the Cambrian record is the action of an “intelligent designer” instantaneously creating phyla. Had the filmmakers bothered to read my book On the Origin of Phyla, they would have understood that I do not support a creationist interpretation of the Cambrian explosion or the fossil record. Scientific findings in many fields, including my own (paleobiology) as well as geology, geophysics, geochemistry, developmental biology, and systematics, have led to a synthesis of the events surrounding the Cambrian explosion that is in full accord with well-established evolutionary principles.

When watching Darwin’s Dilemma, I ask viewers to note:

My interview statements do not criticize evolution
My interview statements do not promote creationism or intelligent design
Even though my interview is interspersed with several intelligent design advocates, I do not share their interpretation of the Cambrian record

I would like viewers to know:
I think evolution is the best scientific interpretation of the fossil record
While the religious views of individuals should be respected, scientists also merit respect earned by generations of hard work in their fields.
Dr. James Valentine
University of California,
Berkeley

Apparently the film makers also forgot to tell Simon Conway Morris (who also appears in the film) the true reason for the interview and intent of the film.

So the experts on palaeontology and palaeobiology that appear do not support the central creationist tenet of the film, which is why, of course, they have Prof Chien as the spokesperson - someone with no background in palaeontology or palaeobiology.

What is it with creationism film makers and their inability to tell the truth about their intentions?

The Cambrian Explosion, the Discovery Institute, and Prof Paul Chien

2009-10-04T20:39:00.006+11:00

Paul Chien is a marine biologist at the University of San Francisco and Discovery Institute fellow. According to the USF website, “Prof. Chien is interested in the physiology and ecology of inter-tidal organisms. His research has involved the transport of amino acids and metal ions across cell membranes and the detoxification mechanisms of metal ions”. While the movie presents him as someone who has “done research in the renowned fossil beds of Chengjiang, China”, there’s no evidence to suggest that Chien is a palaeontologist or that he has published any of this findings (outside of Discovery Institute publications). In the movie, Chien is shown visiting the Chengjiang site. If you listen carefully to the what is said, it appears that he did so simply as an interested member of the public, not as an involved researcher. But the viewer is left with the distinct impression that he worked at the site. The movie’s website goes further, claiming that “Dr. Chien has done research in the renowned fossil beds of Chengjiang, China”. While this is possible, I saw nothing in the movie that actually supports this assertion.

Ian's not alone. I couldn't find any publications in peer-reviewed science journals by Prof Chien on the Chengjiang fauna. However, I'd be pleased to list them here if anyone knows of any.

It appears that Prof Chien is not a palaeontologist, he has no palaeontology experience, he has done no palaeontological research. Prof Chien is not an evolutionary biologist, nor a paleobiologist.

And Nigel Hughes says, “As far as I know, P.K. Chien is not a paleontologist and has published no peer-reviewed papers in paleontology. He is not a ‘player’ in scientific issues related to the Cambrian radiation”. David Bottjer observed that “Chien has tried to produce straight science papers on the Chengjiang fossils, but so far I don’t believe that there have been any publications. He has a Chengjiang fossil collection . . . but even if he does have a lot of specimens, that is not proof that he has or can do anything scientific with them; lots of amateurs (non-scientist) individuals have large fossil collections. From my interactions with him in China I can say that Chien knows nothing about the science. He is interested in creationist goals. (Forrest and Gross 2005 p. 56)

So why is Prof Chien used?

According to Kevin Padian, curator of the Museum of Paleontology and professor of paleontology and evolutionary biology at the University of California-Berkeley “Dr Chien admits that he has no expertise or training in paleontology. He admits in interviews that he came into the issue believing that evolution is not true (Forrest and Gross 2005 p. 56)

Prof Chien is also a CSC Fellow of the Discovery Institute, and has translated Phillip Johnson's book Darwin on Trial into Chinese. Prof Chien is the Discovery Institute's spokesperson for Early Cambrian Chinese fossils because noone with actual experience would associate with the Institute and Intelligent Design

Hmm. So having Prof Chien as a spokesperson for Early Cambrian Chinese fossils is kind of like having Orly Taitz as a spokesperson for the legality of the Obama Presidency. No, that’s not fair, at least Orly has legal qualifications, but this is the Discovery Institute.

Forrest, B. and Gross, P.R. (2005) Creationism's Trojan horse: the wedge of intelligent design. Oxford University Press.

The Cambrian Explosion, the Discovery Institute, and Cambrian Ediacaran Extinction

2009-10-04T13:20:00.008+11:00

While the movie spends a lot of time on the Doushantuo microfossils, little is said about the remainder of the Ediacaran fauna. They’re basically characterised as outliers, unusual organisms that bear little relation to the groups of organisms present in the Cambrian. And they were said to have disappeared before the beginning of the Cambrian.

So the Ediacaran fauna became extinct prior to the Cambrian. Anyone want to bet that the Ediacaran fauna became extinct before the Cambrian? Anyone? Anyone want to put their money where the Discovery Institute’s mouth is? Anyone? No? Aww . . . you people are no fun. Either that or you’ve learned about the Discovery Institute.

Ediacara-type fossils are rare in the southwestern United States, and Cambrian occurrences of soft-bodied Ediacaran-type fossils are extremely rare. We report both discoidal and frondlike fossils comparable to Ediacaran taxa from the western edge of the Great Basin. We describe one specimen of a discoidal fossil, referred to the form species ?Tirasiana disciformis, from the upper member of the Lower Cambrian Wood Canyon Formation from the Salt Spring Hills, California. Two fragmentary specimens of frond-like soft-bodied fossils are described from the middle member of the Lower Cambrian Poleta Formation in the White Mountains, California, and the upper member of the Wood Canyon Formation in the southern Kelso Mountains, California. On the basis of similarities with fossils from the lower member of the Wood Canyon Formation and from the Spitzkopf Member of the Urusis Formation of Namibia, these specimens are interpreted as cf. Swartpuntia. All fossils were collected from strata containing diagnostic Early Cambrian body and trace fossils, and thus add to previous reports of complex Ediacaran forms in Cambrian marine environments. In this region, Swartpuntia persists through several hundred meters of section, spanning at least two trilobite zones. (Hagadorn et al 2000)

Hagadorn, J.W., Fedo, C.M. and Waggoner, B.M. (2000) Journal of Paleontology. 74(4). p.731-740

The Cambrian Explosion, the Discovery Institute, and Cambrian Diversity

2009-10-04T12:54:00.005+11:00

Although the Chengjiang fauna is about 10 million years older than those of the Burgess Shale, it is described as being more diverse. This, the movie argues, narrows the window of time in which these distinct groups of species could have evolved. The shorter the window of time, the less likely it is that these groups would have evolved “by chance”.

OK, to describe the difference in diversity between the two faunas as anything meaningful is to look at the issue purely from a simplistic, superficial view. But then Intelligent Design is a monument to the superficial viewpoint, based as it is on the idea that, ‘gee willikers, that there fla-gell-um looks toooo complex to have e-volved, it must have been de-signed’.

Detailed investigation (i.e. science) is the antithesis of the Art of the Superficial. Detailed investigation blew away the myth that the flagellum was irreducibly complex, and showed that it was similar to a type III secretion system.

Detailed investigation shows that the Chengjiang fauna is more diverse that the Burgess Shale fauna for reasons that have nothing to do with the diversity of life at the time. It is known that the Burgess Shale fauna, while spectacular, is a restricted fauna. It does not represent the breadth of life at the time. The fauna has been washed in over a steep limestone escarpment into deep, oxygen poor, water over 160 metres deep (see for example Briggs et al 1994).

The Chengjiang fauna, while also predominately a washed-in fauna, was positioned in open water at the foot of a delta at around 100 metres deep (see for example Chen and Zhou 1997, Hou et al 2004). A much more open system and so would be expected to sample a greater range of organisms.

One datum point from one location in Chengjiang and Burgess Shale time does not tell us about overall diversity during either time, unless you use the Art of the Superficial.

Briggs, D.E.G., Erwin, D.H. and Collier, F.J. (1994) The Fossils of the Burgess Shale. Smithsonian Institute Press. 238pp.

Hou, X-G; Aldridge, R.J., Bengstrom, J, Siveter, D. J., Feng, X-H (2004) The Cambrian Fossils of Chengjang, China. Blackwell Science. 233pp.

Junyuan Chen and Guiqing Zhou (1997) Biology of the Chengjiang fauna. Bulletin of the National Museum of Natural Science. 10. p.11-106.

The Cambrian Explosion, the Discovery Institute, and Charles Doolittle Walcott

2009-10-03T14:58:00.008+10:00

The Discovery Institute is back with another attempt to legitimize Intelligent Design, this time with a movie on the Cambrian Explosion - Darwin’s Dilemma.

I haven’t seen the film, but given the well documented problems the Discovery Institute and its cohorts seem to have with basic honesty, I’m expecting the usual snow job.

I intend to write a set of blog posts addressing the comments and thoughts on Darwin’s Dilemma from people who have seen the film. This is useful because people who do not have a background in the Cambrian Explosion or palaeontology are the people that the Discovery Institute is hoping to mislead. So what such people are taking away from the film, the messages that the Discovery Institute is hoping to instill, the questions raised in people’s minds, etc., are worth addressing.

This post is in response to Ian’s comments here, to address what appears to be a misleading section in the film regarding Charles Doolittle Walcott (the discoverer of the Burgess Shale) and alleged contemporary geological ideas as to the whereabouts, and lack, of Precambrian fossils.

Ian writes:

According to the movie Walcott (the discovered of the Burgess Shale) suggested that the transitional Precambrian fossils might be found beneath the ocean floor. I have no idea whether this was a serious prediction or not, but the movie treats it as if it were. They say that Walcott’s hypothesis remained untested until deep-water drilling for oil has brought lots of drill cores from the bottom of the ocean, and none have revealed Precambrian fossils. They then go on to say that ocean-floor mapping has revealed that the rocks of the ocean floor are relatively young, and the ocean floor is an entirely unsuitable place to look for Precambrian fossils.

So is this correct? Well, the first part is – but needs some clarification (surprised?), but the rest is pure bollocks.

Firstly did Walcott suggest that Precambrian fossils would be found beneath the ocean floor? Well, yes he did, but deep under the ocean, not necessarily deep under the ocean floor. This was in response to his being unable to find Precambrian fossils.

I have for the past 18 years watched the geological and paleontological evidence that might aid in solving the problem of Precambrian life. The great series of Cambrian and Precambrian strata in eastern North America from Alabama to Labrador in western North America from Nevada and California far into Alberta and British Columbia, and also China, have been studied and searched for evidences of life until the conclusion had gradually been forced upon one that on the North American continent we have no known Precambrian marine deposits containing traces of organic remains, . . . (Walcott 1910, p.2)

To explain this Walcott suggested that the Precambrian continents were much greater in extent than the present, or even the Cambrian, continents, and so the Precambrian ‘coastlines’ – and hence shallow water marine sediments to look for fossils – were much further out to sea compared with the current coastline. In other words, the current continents are the centres of the Precambrian continent and represent

. . a period of continental elevation and largely terrigenous sedimentation in non-marine bodies of water, also a period of deposition by aerial and stream processes over considerable areas (Walcott 1910, p.4)

Walcott hypothesized a much larger Precambrian continent to account for the lack of marine Precambrian sediments because he was working in a time before the theory of plate tectonics revolutionized our understanding of continental processes. In Walcott’s time the continents were considered stationary, and so a lack of sediments represented a period of uplift and wider continents, whereas the presence of marine sediments represented a period of subsidence and seas inundating the margins of the continents.

So Walcott considered that the margins of the Precambrian continent were much further out in the oceans that the present continental margin, and hence the shallow marine sediments with Precambrian fossils would be found under the deep ocean. This period of unknown marine sedimentation was named the Lipalian period. But Walcott’s hypothesis and the Lipalian period was short lived.

Which brings up to the second claim, that Walcott’s hypothesis remained untested until deep-water drilling for oil has brought lots of drill cores from the bottom of the ocean, and none have revealed Precambrian fossils.

Say what?!

Umm, Walcott’s hypothesis of the Lapilian period of non-deposition was largely ignored,

Despite Walcott's diligent search, hardly any fossils were found in these older strata, and those discovered did not assist in biostratigraphy. Years later, when attempting to explain the issue of a diverse Cambrian fauna seemingly without any antecedents, Walcott developed a hypothesis to explain the absence of earlier fossils based on geological, rather than biological, features. He suggested that a widespread unconformity at the top of the Proterozoic represented an interval oftime, the Lipalian, in which such an earlier fauna developed elsewhere, but was not recorded in any outcrop. The concept of naming a gap to represent a major missing segment of geologic time, did not result in any comment from the geologic community and the Lipalian Interval vanished. (Yochelson 2006)

Walcott was doing science. He had observations – apparent lack of marine Precambrian sediments – and produced a hypothesis to account for them. But the hypothesis was not taken up. It was, however, tested, albeit indirectly.

By the late 1950 and early 1960’s the theory of sea floor spreading was becoming well established and by the end of the 1960 it was shown that the ocean floor was younger than Precambrian through measuring the magnetic striping caused by magnetized lava formations (see for example Heirtzler 1968). See floor spreading and plate tectonics rendered any vestige of Walcott's hypothesis redundant.

So, far from waiting until deep sea coring (not incidentally related to oil exploration, but to the Joint Oceanographic Institutions for Deep Earth Sampling, Ocean Drilling program in the mid 1980’s), it has been well known that there are no Precambrian rocks awaiting discovery under the deep oceans for at least 40 years.

But the Discovery Institute film also neglects the fact that fossil-bearing marine Precambrian rock had been discovered before this: Charnwood Forest, England (Ford 1958); South Australia and Namibia (Glaessner 1959); and subsequently from Canada, Russia, and the USA.

To suggest that Walcott's hypothesis wasn't tested, or that palaeontologists were somehow hanging out for deep sea cores to provide Precambrian fossils, is laughable, but this is the Discovery Institute.

Ford T.D. (1958) Precambrian fossils from Charnwood Forest. Proceedings of the Yorkshire Geological Society. 31. p.211-217

Glaessner, M (1959) Precambrian Coelenterata from Australia, Africa and England. Nature. 183. p.1472-1473.

Heirtzler, J.R. Sea Floor Spreading. Scientific American, December 1968, p.60-70.

Walcott, C.D. (1910) Abrupt appearance of the Cambrian fauna on the North American Continent. Cambrian Geology and Paleontology II. Smithsonian Miscellaneous Collections 57. p.1-16.

Yochelson, E.L. (2006) The Lipalian interval: A forgotten, novel concept in the geologic column. Earth Science History. 26(2), p.251-269.

Vale Troy Kennedy Martin

2009-09-29T18:17:00.003+10:00

On 15 September, Troy Kennedy Martin died of liver cancer.

He wrote two movies Kelly's Heros and The Italian Job (the proper one with Michael Cane, not the pale imitation). But for me he is best remembered as the writer of the ground-breaking 1985 BBC TV drama Edge of Darkness. Also known for it's music score co-written and played by Eric Clapton (see below), Edge of Darkness marked the beginning of real political drama on the BBC.

If you've never seen it, do yourself a favour, get a copy, shut the curtains, turn off the phone and settle down for 5 hours of the best TV drama you are ever likely to see.

Livelife 2

2009-09-08T22:01:00.003+10:00

Hi Ho. Hi Ho. It's off to work we go . . .

Geologists always walk around looking at the ground because that's where the rocks are. Especially in a creek bed in the middle of a gorge in the Flinders Ranges. Occasionally you see something else of interest.

This group boldly heading out along the floor of the gorge took me by surprise because, although there are several species of butterflies and moths native to the Flinders, I'd never seen caterpillars there before (click on the image to enlarge). The ripples in the creek bed can clearly be seen, and the trail of caterpillars almost mimics the rise and fall of the ripples. The lens cap is 52mm in diameter

2010 Atheist Global Convention

2009-08-18T21:06:00.003+10:00

The 2010 Atheist Global Convention will be held down under in Melbourne. Speakers include Richard Dawkins and Philip Adams.

They are currently taking expressions of interest to estimate numbers, so go over to the site and express yours. Oh yeah, someone called PZ Myers will also be there.

The Wilkins will also probably be there. He will even sign his book if you ask him.