Ophiolycus Mortensen, 1933

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 : 103-106

Genus Ophiolycus Mortensen, 1933

Figures 27Q–U; 71–74

Ophiolycus (as subgenus of Ophioscolex ): Mortensen, 1933b: 315

Type species: Ophioscolex dentatus Lyman, 1878 , by original designation

Diagnosis. The disk is covered with numerous small, uniform scales, conspicuous when dried, covered by a thin skin layer. The radial shields are moderately developed, elongated, visible in dried specimens. The adradial genital plate is well developed, tightly articulating with the radial shield, proximally slightly curved. The abradial genital plate is short and externally only slightly conspicuous. The articulation surface of the adradial genital plate is an elongate elevation with a small pit dorsally. The articulation surface of the radial shield is a slightly prominent elevation with distinct proximal groove. The genital slits are long; genital plates bordering about two thirds of the slits. The jaw bears numerous spiniform oral papillae, similar in shape to the cluster of the 3–4 ventralmost teeth. Two adoral shield papillae and one adjacent oral papilla of each jaw are spiniform, approximately 2 times as long as the oral papillae, placed around the second tentacle pore. The half-jaws are slightly elongated. The adradial sides of the jaws bear a few sharp straight folds distally. The dental plate is small, elongated, entire, without folds and with few rounded sockets, alternately placed. The teeth are spiniform and few in number (besides the apical papillae there are 4–5 teeth). All teeth are of similar shape. The oral shield is rhomboidal, almost devoid of a distinct distal lobe. The adoral shields have distal bilobed wings and are proximally very narrow bars. Dorsal arm plates are moderately developed in some segments but fragmented proximally. Ventral arm plate is well defined. The arm spine articulations are placed almost parallel in relation to the lateral plate. The muscle and nerve openings are similar in size. A low perforated lobe occupies the dorsal part of the articulations. The sigmoidal fold is absent. The spines are relatively long, flattened, solid over almost their entire length, containing only a small lumen. Distally the dorsal and middle arm spines transform into hooks. One small spiniform tentacle scale is placed on the lateral arm plate. The vertebrae have a broad dorsal keel, with a blunt end; the dorsal medial suture is indistinct. The articulation is zygospondylous. The podial basins are large.

Material studied. Ophiolycus dentatus ( Lyman, 1878) , ZMUC, 3 specimens ( Figs 71–72); Ophiolycus purpureus, ZMMU D-845, 11 specimens; Mareano, 3 specimens ( Figs 73–74); Ophiolycus nutrix Mortensen, 1936 , ZMMU D-818, 2 specimens ( Figs 27S–U) .

Remarks. One of the characteristic external features of the genus Ophiolycus was the presence of hooks on the distal arm segments ( Mortensen 1933b; 1936) ( Figs 71H; 73J), whereas the type species of the genus Ophioscolex , O. glacialis does not possess hook-shaped spines on the distal segments. However, well-defined hooks on the distal arm segments are apparently widely distributed within various distantly-related taxa of the family Ophiomyxidae . In the present study, true distal hooks were detected in the genera Ophiomyxa and Ophiobyrsa ( Figs 1L; 79J). Ophiosyzygus disacanthus H.L. Clark, 1911 , also has on the distalmost segments small hook-shaped spines ( Figs 71I; 75J), somewhat different from the typical hooks of Ophiomyxa and Ophiobyrsa . Thus, the hooks or hook-shaped spines are clearly a convergent feature. Besides hook-shaped spines, the genus Ophiolycus is well distinguished from the genus Ophioscolex , and the restricted diagnosis of both genera are given above.

O’Hara (pers. comm.) suggested that Ophiolycus farquhari McKnight, 2003 may be a synonym of Ophiologimus quadrispinus H.L. Clark, 1925 . Ophiolycus farquhari is externally similar to Ophiologimus quadrispinus in general appearance of the disk and arms, elongate radial shields and absence of the long adoral shield papillae. The latter feature is diagnostic for all species of the genus Ophiolycus . McKnight (2003) mentioned the distalmost spines as “weakly hooked at the tip”. Both the type species of the genus Ophiologimus , O. hexactis ( Fig. 48F), and other studied material of O. quadrispinus reveal the presence of well-defined hooks. “ Ophiolycus ” farquhari therefore is not included into the genus Ophiolycus here, but until a complete revision of the genus Ophiologimus will be performed, it is retained as a species of doubtful status.

Number of species: 3.