Friday, May 27, 2011

An Ordovician Anomalocaridid

A giant Ordovician anomalocaridid. 2010. P. Van Roy and. E.G. Briggs. Nature 473: 510–513.

Image: Esben Horn
Scientists have discovered a giant fossilized anomalocaridid from the Ordovician that measures one meter in length meaning these animals existed for 30 million years longer than previously realized.
Anomalocaridids were the largest animals of the Cambrian period, known for the "Cambrian Explosion" that saw the sudden appearance of all the major animal groups and the establishment of complex ecosystems about 540 to 500 million years ago.

Fossils from this period suggested these marine predators grew to be about two feet long. Until now, scientists also thought these strange invertebrates—which had long spiny head limbs presumably used to snag worms and other prey, and a circlet of plates around the mouth—died out at the end of the Cambrian.

The anomalocaridid fossils reveal a series of blade like filaments in each segment across the animal's back, which scientists think might have functioned as gills.

The specimens are just part of a new trove of fossils from Morocco that includes thousands of examples of soft-bodied marine fauna dating back to the early Ordovician period, 488 to 472 million years ago. The animals found in Morocco inhabited a muddy sea floor in fairly deep water, and were trapped by sediment clouds that buried them and preserved their soft bodies. link