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Sunday, December 26, 2010

Cambrian explosion: Let's just say that the Echinoderm family goes back a long way ...

British physicist David Tyler comments on new findings that intensify the impact of the Cambrian explosion of life forms, about 550 million years ago:
Echinoderm diversity traced back to Lower Cambrian

Some have argued that echinoderm diversity is an Ordovician phenomenon: linked to the Great Ordovician Diversification. Others make the case for the radiation to have initiated earlier. All seem to be agreed that the origin of echinoderms is shrouded in uncertainty. One major problem is that the relevant fossils are unfamiliar and often poorly preserved and there are often doubts about their classification. However, in June 2010, research was reported dealing with Middle Cambrian echinoderms from Spain.

"The new Spanish data suggest that a number of the clades involved in [the Great Ordovician] diversification (such as sucocystid cinctans, cothurnocystid stylophorans, ctenocystoids, and isorophid edrioasteroids) appeared significantly earlier in Gondwanan settings than previously thought. This shows that, even by the earliest middle Cambrian, a variety of novel body plans and ecological strategies already existed among echinoderms, pushing back the timing of important divergences into the lower Cambrian."

One of the Spanish fossils
A Middle Cambrian echinoid - a stromatocystitid edrioasteroid (source here)

For more, go here.


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