The Thylacocephala (from the Greek thylakos, meaning "pouch", and cephalon meaning "head") is a recently recognized extinct group of uncertain, but probably crustacean, affinity, comprising fossils formerly assigned to many different crustacean groups. Of the features which could prove crustacean affinities, the arrangement of mouthparts would be the easiest to find in the Thylacocephala. The literature features some mention of such a head arrangement, but none definitive. These fossils were ver