Aegirocassis

Aegirocassis is an extinct genus of giant radiodont arthropod belonging to the family Hurdiidae that lived 480 million years ago during the early Ordovician in the Fezouata Formation of Morocco.

[3] This animal is characterized by its long, forward facing head sclerite, and the endites on its frontal appendages that bore copious amounts of baleen-like auxiliary spines.

[1] This animal evolving filter-feeding traits was most likely a result of the Great Ordovician Biodiversification Event, when environmental changes caused a diversification of plankton, which in turn allowed for the evolution of new suspension feeding lifeforms.

Several details seen clearly in the specimen led to a review and reassessment of research of existing specimens and, most importantly, to the conclusion that the ventral pair are homologous with arthropod endopods (limb-like inner branches) and lobopodian limbs (lobopods), and the dorsal pair are homologous with the flaps of gilled lobopodians and exites (gill-like outer branches) of the arthropod biramous limb.

[13] Aysheaia Onychodictyon Tardigrada Onychophora Megadictyon Jianshanopodia Hadranax Kerygmachela Pambdelurion Utaurora Opabinia Aegirocassis Peytoia Schinderhannes bartelsi Cambroraster Hurdia Amplectobelua Lyrarapax Anomalocaris Houcaris Deuteropoda

Reconstruction of the Fezouata Biota, featuring roughly 50 different species. The largest animal, Aegirocassis benmoulai (just over 2 metres in length), is depicted in a pair swimming just above the seafloor. [ 11 ] The pair is depicted as sexually dimorphic, with the larger individual possessing an expanded lateral process on its central head carapace. [ 1 ]