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Ophiocistioidea; Temporal range: Ordovician–Carnian 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

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]

Etymology

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

Anatomy

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]

References

^ Reich & Haude 2004
^ ^a ^b Reich et al. 2018
^ Rahman et al. 2019, pp. 4–6
^ Nanglu et al. 2023, p. 331
^ Ubaghs 1966
^ Smith & Reich 2013, pp. 677–678
^ Rahman et al. 2019, pp. 2–4

Works cited

Nanglu, Karma; Cole, Selina R.; Wright, David F.; Souto, Camilla (2023). "Worms and gills, plates and spines: the evolutionary origins and incredible disparity of deuterostomes revealed by fossils, genes, and development". Biological Reviews. 98: 316–351. doi:10.1111/brv.12908.
Rahman, Imran R.; Thompson, Jeffrey R.; Briggs, Derek E. G.; Siveter, David J.; Siveter, Derek J.; Sutton, Mark D. (2019). "A new ophiocistioid with soft-tissue preservation from the Silurian Herefordshire Lagerstätte, and the evolution of the holothurian body plan". Proceedings of the Royal Society B. 286 (1900). doi:10.1098/rspb.2018.2792. PMC 6501687.
Reich, M.; Haude, R. (2004). "Ophiocistioidea (fossil Echinodermata): an overview". Echinoderms: München. London: Taylor & Francis. pp. 489–494. doi:10.1201/9780203970881.ch82 (inactive 2024-11-12).{{cite book}}: CS1 maint: DOI inactive as of November 2024 (link)
Reich, Mike; Stegemann, Tanja R.; Hausmann, Imelda M.; Roden, Vanessa J.; Nützel, Alexander (2018). "The youngest ophiocistioid: a first Palaeozoic-type echinoderm group representative from the Mesozoic". Palaeontology. 61 (6): 803–811. doi:10.1111/pala.12392.
Smith, Andrew B.; Reich, Mike (2013). "Tracing the evolution of the holothurian body plan through stem-group fossils". Biological Journal of the Linnaean Society. 109 (3): 670–681. doi:10.1111/bij.12073.
Ubaghs, Georges (1966). "Ophiocistioids". In Moore, Raymond C. (ed.). Treatise on Invertebrate Paleontology, Part U: Echinodermata 3. University of Kansas Press. pp. U174 – U188. Retrieved 28 October 2024.