Thylacocephala

Abstract

AbstractThe infraclass Thylacocephala features marine predatory, or scavenging, arthropods that populated the seas from at least the Early Silurian to the Upper Cretaceous. The name “thylaco-cephala” refers to the sac-like (or bag-like, or pouch-like) head seen on many of the larger, better preserved species, which arises from an extreme hypertrophy of the compound eyes. Assessing the higher affinities and determining the internal phylogeny of thylacocephalans have proven difficult. This chapter advances hypotheses that the body tagmosis patterns could be either 5–8–0, or 5–8–8, although the Silurian Thylacares might be 5–8–14. Hence, they filled an effective role in the Paleozoic and Mesozoic seas as rapacious carnivores. It is suggested that they be possibly assigned to subclass Malacostraca.