Aegirocassis
Early Ordovician (Arenigian)
Fezouata Formation
Mecissi-Zagora Region, Draa Valley
Morocco

A spectacular large Aegirocassis appendage, an extraordinary Ordovician anomalocaridid and one of the largest known members of this remarkable group. Aegirocassis was a giant filter feeder that used its specialized head appendages to collect tiny organisms from the water. This specimen preserves an impressive example of its feeding anatomy and is presented fully on a substantial slab.
Large 80mm anomalocarid appendage on 220mm slab

Aegirocassis is a genus of anomalocaridid known only from the Early Ordovician of Morocco. It was one of the largest of all arthropods that ever lived, reaching about 6 1/2 feet long and was almost certainly the largest animal of its time. Like the largest animal of our time, the blue whale, it has been determined to have been a filter-feeder that descended from predatory ancestors.

For decades anomalocaridids were assumed to have died out by the end of the Cambrian until one was discovered in the Early Devonian of Germany.

Have a look at this amazing 3D model of Aegirocassis courtesy of Google and darwinmuseum.ru. Click on the arrows at the bottom right corner to see it full screen!