Ophiocistioidea is a class of extinct echinoderms from the Palaeozoic and early Mesozoic. They most likely form a paraphyletic grade along sea cucumber stem lineage, although some sources still consider the question of ophiocistioid monophyly unresolved.
Etymology Ophiocistioidea is named from the Greek words ὄφις (ophis) "snake" and κίστη (kiste) "box".
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. 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.
Phylogeny The skeletal structure, close to that of sea urchins (and sea cucumbers for some soft species.), often places these animals in Echinozoa. However, the data are still insufficient to finally decide on this case: the study of particularly well-preserved fossils suggests that Ophiocistioidea could be the ancestor group of sea cucumbers..
At present, about 40 species have been identified. (10 are from the Devonian, which seems to be the golden age of this group), categorized into 17 genera and 6 families. Most of the fossils have been found in North America and Europe, with some in Australia.
List of families and genera from Reich & Haude (2004) Family Volchoviidae Hecker, 1938 genus Volchovia Hecker, 1938 Family Eucladidae Gregory, 1896 genus Eucladia Woodward, 1869 genus Anguloserra Haude & Langenstrassen, 1976 Family Sollasinidae Fedotov, 1926 genus Sollasina Fedotov, 1926 genus Euthemon Sollas, 1899 genus Cardioserra Romanek, 1984 genus Klukovicella Prokop & Petr, 1987 Family Rhenosquamidae Richter, 1930 genus Rhenosquama Richter, 1930 genus Gillocystis Jell, 1983 Famille Rotasacciidae Haude & Langenstrassen, 1976 genus Rotasaccus Haude & Langenstrassen, 1976 [ 1976b] genus Erisserra Boczarowski,2001 genus Longiserra Boczarowski, 2001 genus Ornatoserra Boczarowski, 2001 genus Pararotasaccus Kozur &Mostler, 1989 Family Linguaserridae Reich & Haude 2004 genus Linguaserra Langer, 1991
Gallery
See also List of echinoderm orders
References
Works cited