Massive Fossil Fills in Arthropod’s Evolutionary Gaps

posted: 03/11/15
by: Discovery.com Staff
Aegirocassis benmoulae
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An artist rendering of 7-foot-long Aegirocassis benmoulae in its heyday.
Reconstruction by Marianne Collins, ArtofFact

A fossil of a massive, 7-foot-long sea creature is helping scientists better understand the evolutionary history of arthropods. The striking organism, dubbed Aegirocassis benmoulae, is believed to be the largest anomalocaridid (arthropods' evolutionary precursor) to ever exist.

Paleontologists have long wondered how modern arthropods, such as spiders and lobsters, developed legs, and A. benmoulae is filling in the gaps in our understanding. The fossil shows two distinct sets of lower flaps, used for swimming, that are believed to be the predecessor to legs. Until now, a full anomalocaridid fossil had never been recovered.

The ocean was teeming with A. benmoulae during the Ordovician period, a time of "massive increases in ecological complexity," explained lead author Peter Van Roy, a paleontologist at Yale University. It was also during this period that animals began to venture out of the ocean and onto land.

Although it was discovered in 2011, the fossil required 500 hours of excavation before it could be completely and thoroughly examined.

Click here to read the full story on PBS.org


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