Ophiogaleus, Thuy, 2013

Thuy, Ben, 2013, Temporary expansion to shelf depths rather than an onshore-offshore trend: the shallow-water rise and demise of the modern deep-sea brittle star family Ophiacanthidae (Echinodermata: Ophiuroidea), European Journal of Taxonomy 48, pp. 1-242 : 108-109

Genus Ophiogaleus gen. nov.

urn:lsid:zoobank.org:act:25557BA8-022E-49DC-99A2-ACA17793A5EB

Type species

Ophiacantha ? constricta Hess, 1966, by present designation.

Other species included

Ophiacantha? danica Rasmussen, 1952 ; Ophiacantha? dorecki Hess, 1962 and Ophiogaleus stans sp. nov.

Diagnosis

Ophiacanthid genus with numerous (generally at least seven) ear-shaped spine articulations on strongly elevated distal portion of LAP; dorsal and ventral lobes of spine articulations merged into continuous lobe; outer surface with moderately coarsely meshed stereom; ridge on inner side composed of short, narrow, oblique central part with generally strongly widened, triangular dorsal portion with nearvertical distal edge and pointed dorsal and ventro-proximal tips; generally several spurs at least on inner distal edge of LAPs; arm spines forming fan dorsally at least in proximal arm segments; row of spine articulations commonly protruding ventrally.

Etymology

Genus named in honour of my friend and colleague Andy Scott Gale for his continuous and encouraging support, the delightfully shared delicacies and wines, and for providing some of the most important

samples used in the present study; from ophis, Greek for “snake”, a commonly used prefix for ophiuroid names, gender masculine.

Remarks

Ophiacanthid fossil occurrences based exclusively on dissociated LAPs were almost invariably assigned tentatively to the genus Ophiacantha using open nomenclature ( Thuy et al. 2012, plus references therein) following Hess’s (1962) suggestion to use the type taxon of a family in case of uncertain generic placement. Although assignment of the present species to the genus Ophiacantha is shown here to be untenable (see above), some of the other species, including Ophiacantha ? constricta and Ophiacantha ? danica, display LAP morphologies which are very close to that of Ophiacantha in its proper sense. These similarities pertain mainly to the shape and position of the spine articulations and the shape of the ridge on the inner side of the LAPs. In fact, the relatively short, oblique central part with the strongly widened, triangular dorsal part displaying a near-vertical distal edge and pointed dorsal and ventroproximal tips observed in the fossil LAP types in question can be considered as a variant of the ridge observed in Ophiacantha bidentata and similar extant congeners. In the latter, the ridge is composed of a long main, oblique, straight to slightly bent part displaying a generally relatively long ventrally pointing extension. In some cases, the main part and its ventrally pointing extension are fused into a large, neartriangular knob, which then looks very similar to the ridge observed in the fossil LAP types in question, except that in the latter there is a kink between the non-widened part of the ridge and the large triangular dorsal part.

In spite of the striking similarities, in particular with respect to the shape of the ridge, the fossil LAPs in question differ from the LAPs of Ophiacantha in displaying several spurs on the inner distal and, to a lesser extent, the outer proximal edge. In combination with the above-mentioned kink between the narrow central part of the ridge and its strongly widened, triangular part, this difference warrants separation at the generic level. Ophiogaleus gen. nov. is thus introduced here to accommodate the fossil LAPs in question. It must be stressed, however, that the striking similarities in LAP morphology strongly suggest that Ophiogaleus gen. nov. and Ophiacantha are phylogenetically very close.