Friday, November 5, 2010

Lower Cambrian Sea Anemones from China

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

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