Description

Anomalocaridid appendage

Early Ordovician

Upper Fezouata Formation

Zagora, Morocco.

35mm appendage on 97mm slab.  Exceedingly rare in the Ordovician.

Anomalocaridids are a group of actively-swimming arthropods (Suborder Anomalocaridida) best known from the Cambrian but surviving into the Devonian.  In the Cambrian they were the largest predators on earth at about 3 feet in length.  In the Ordovician one form was twice the size but had evolved into a filter-feeder.

Once thought to have died out by the end of the Cambrian, an anomalocaridid was described from the Early Devonian of Germany (Hunsruck Shale) in 2009.