Ophiocymbium Lyman, 1880

Martynov, Alexander, 2010, Reassessment of the classification of the Ophiuroidea (Echinodermata), based on morphological characters. I. General character evaluation and delineation of the families Ophiomyxidae and Ophiacanthidae 2697, Zootaxa 2697, pp. 1-154 : 52-53

Genus Ophiocymbium Lyman, 1880

Figures 4E–G, H, L, T; 12C–G; H, M; 15B; 17D, E, G–H, J, P, S; 27H–I; J, K; 40–43; 55 I–N; 67G

Ophiocymbium Lyman, 1880: 7

Type species: Ophiocymbium cavernosum Lyman, 1880 , by monotypy

Diagnosis. The disk is covered with numerous small, uniform scales covered by a thin skin layer, not evident when dried. The dorsal disk surface can bear a few sparsely placed spinelets. The radial shield and adradial genital plate are small and externally inconspicuous or totally absent. The articulation surface of the radial shield is distinctly excavated ventrally, distally with a groove. The abradial genital plate is absent. The genital slits are small. The jaws bears a few block-shaped oral papillae. The adoral shield papillae, if any, differ considerably from the oral papillae and are placed around the second tentacle pore. The jaws are slightly elongated. The distal adradial sides of the jaws bear a few sharp straight folds. The dental plate is entire, small, with a few rounded sockets and devoid of folds. The teeth are spiniform and numerous, ventralmost teeth (apical papillae) of similar shape. The dorsal and ventral arm plates are well developed. The tentacles scales are placed on the lateral arm plate, and usually occur only on a few proximal segments. The arm spine articulations are compressed transversally. Some proximal articulations may have a distinct nerve opening. The sigmoidal fold is absent. The arm spines are relatively short and flattened, hollow. Distal hooks absent. The vertebrae with a blunt distal keel and zygospondylous articulation.

Remarks. Until recently, this genus was monotypic ( Lyman 1880; Paterson 1985). In the present study four other abyssal and ultra-abyssal new species have been discovered. This facilitates an appropriate discussion on the variability of different features within the genus. The taxonomic placement of Ophiocymbium will be evaluated after a general discussion on the taxonomic value of ophiuroid characters. R/ V “Akademik Kurchatov” ultra-abyssal sampling in the Sandwich trench discovered another unknown ophiuroid, seemingly belonging to the family Ophiacanthidae , and similar to the genus Ophiocymbium . Close examination suggests that it is an undescribed genus and species, named here Ophioplexa condita gen. et sp.

nov. It is of importance for the present study since, like Ophiocymbium , it apparently belongs in Ophiotominae and simultaneously has affinities to Ophiomyxidae . It will be listed and described below.

Number of species in the genus: 5.