Sunday, October 4, 2009

The Cambrian Explosion, the Discovery Institute, and Cambrian Ediacaran Extinction

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 can be found here and here.

This post is in response to Ian’s comments here, and addresses what appears to be a misrepresentation of the Ediacaran fauna.

Ian writes:
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

1 comment:

  1. The cause of Cambrian Explosion is Cognition (Nervous Systems) plus Sexual Selection. See here for more details: