Full Text:
Researchers have uncovered a fossil sea urchin that pushes back a fork in its family tree by 10 million years. A team from the University of Southern California and Caltech found the Eotiaris guadalupensis in the collections of the Smithsonian Institution from the Glass Mountains of west Texas, where it had been buried in a rock formation that dates back to 268.
8 million years at its youngest. Eotiaris guadalupensis is a cidaroid, one of the two main types of sea urchins found in today’s oceans. The other group, the euechinoids, evolved wildly varying body types and accounts for almost all sea urchins alive today. Cidaroids, by contrast, look pretty much the same as they did millions of years ago. Both evolved from an ancestral group of echinoids known as the Archaeocidaridae, which are now extinct. The divergence of the two groups marks a major–and relatively abrupt–shift in the genetic organization of sea urchins.Image credit: Image courtesy of David Bottjer
