Fossil of Giant Ancient Sea Predator Discovered in Morocco

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Paleontologists have discovered that a group of remarkable ancient sea creatures existed for much longer and grew to much larger sizes than previously thought, thanks to remarkably well-preserved fossils discovered in Morocco.

Anomalocaridids had long, spiny head limbs presumably used to snag prey, and a series of blade-like filaments in segments across the animal’s back, which scientists think might have functioned as gills.

Credit: Esben Horn

The creatures, known as anomalocaridids, were already thought to be 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 fossil shows this ancient sea predator existed for much longer and grew to much larger sizes than previously thought.

Credit: Peter Van Roy

Now a team led by Yale postdoc Peter Van Roy (now at Ghent University in Belgium) and Derek Briggs, Director of the Yale Peabody Museum of Natural History, has discovered a giant fossilized anomalocaridid that measures one meter (more than three feet) in length. In addition, the creature dates back to the Ordovician period, a time of intense biodiversification that followed the Cambrian, meaning these animals existed for 30 million years longer than previously realized.