Cheloniellid
Ordovician
Fezouata Formation
Mecissi-Zagora Region, Draa Valley, Morocco.

Huge 155mm (6 inch) cheloniellid arthropod on 320mm (12.6 inch) slab.

Arthropod.

A cheloniellid is an animal that belongs to a group of arthropods, Cheloniellida, which is considered an order but how it fits within the Arthropoda is unclear.  It looked sort of like a flatter pill bug.  Cheloniellids are known from the Late Cambrian to Devonian at sites in North America, Europe, and North Africa..