A paraphyletic grouping of extinct irregular echinoids, members of which gave rise to the Holasteroida and Spatangoida in the Lower Cretaceous. Disasteroids have a split apical disc; the posterior two ocular plates and their associated ambulacra are separated from the remainder of the apical disc (and the anterior three ambulacra) by intercalated inter-ambulacral plates. Disasteroids have a strong bilateral symmetry. Larger pore pairs, arranged in phyllodes around the mouth, suggest that disasteroids were deposit feeders with penicillate feeding tube feet. Most species probably lived infaunally, though not burrowing deeply.
Five families are included: Acrolusiidae, Collyritidae, Disasteridae, Pygorhytidae, and Tithoniidae, separated principally on apical disc plating. Approximately 75 species have been named, arranged in 17 genera. The oldest species is late Bajocian (Middle Jurassic) and the youngest Albian (Lower Cretaceous). The group achieved its greatest diversity during the Upper Jurassic. See also Atelostomata; Echinodermata.
