World's Oldest Fossil Sea Urchin May Reveal More about Evolution

A fossil sea urchin is actually the oldest ever found. In fact, it pushes back a fork in its family tree by a staggering 10 million years.

In this latest study, the researchers looked at a fossil of the species Eotiaris guadalupensis. This animal is a cidaroid, which is one of the two main types of sea urchins found in today's oceans. The other group, called the euechinoids, evolved wildly varying body types and accounts for almost all sea urchins alive today. In contrast, cidaroids look very similar to how they appeared millions of years ago. Both of these groups evolved from an ancestral group of echinoids, known as Archaeocidaridae, which are now extinct.

The divergence of these groups marks a major shift in the genetic organization of sea urchins. Pinning down a time when this occurred, therefore, allows evolutionary scientists to understand the processes that occur during major evolutionary changes.

"This fossil pushes the evolution of this type of sea urchin from the Wuchiapingian age all the way back to the Roadian age," said David Bottjer, one of the researchers, in a news release.

The findings reveal a bit more about when these evolutionary changes occurred. This, in turn, may tell scientists a bit more about the process of evolution in general and allow researchers to understand how the sea urchin family tree branched out and developed over time.

The findings are published in the journal Scientific Reports.

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