Ophiocistioidea

Ophiocistioidea is a class of extinct echinoderms from the Palaeozoic and early Mesozoic.^[2] They most likely form a paraphyletic grade along sea cucumber stem lineage,^[3] although some sources still consider the question of ophiocistioid monophyly unresolved.^[4]

Ophiocistioidea Temporal range: Ordovician–Carnian[1][2] PreꞒ Ꞓ O S D C P T J K Pg N
Restoration of Eucladia woodwardi dorsal (top) and ventral (botoom) views
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Echinodermata
Subphylum:	Echinozoa
Class:	Ophiocistioidea

Etymology

Ophiocistioidea is named from the Greek words "ophis" (snake) and "kiste" (box).^[5]

Anatomy

Sollasina cthulhu

Ophiocistioids had a flattened globular body encased in a solid test of calcareous plates, similar to that of a modern sea urchin. As with sea urchins, the mouth faced downwards and contains a structure known as an Aristotle's lantern. Unlike sea urchins, the anus was laterally placed rather than being at the center of the upper surface. Five ambulacra radiated outwards from the mouth across the lower surface, but only continued around the edge to just under the level of the anus. The madreporite was to one side of the mouth.^[6] Ophiocistioids had unusually long tube feet emerging from near the mouth and around the edges of the body. Unlike the tube feet of other echinoderms, these tube feet were covered in stereom plates.^[7]

See also

• List of echinoderm orders