Ophiojagtus argoviensis Thuy 2013, comb. nov.
Creators: name: Thuy, Ben
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Ophiuroidea
Ophiurida
Ophiacanthidae
Ophiojagtus
Ophiojagtus argoviensis

description: Ophiojagtus argoviensis (Hess, 1966) comb. nov.
Fig. 37: 10-11
Hemieuryale? argoviensis Hess, 1966: 1040, 1052, figs 24-25, 67-69.
Diagnosis
Species of Ophiojagtus gen. nov. with relatively small LAPs displaying a broad and short ventral portion accounting for approximately one-quarter of the total LAP height; proximal edge occasionally with very weak, rounded protrusion; five to six spine articulations with weak dorsalward increase in size and slightly stronger dorsalward increase in the size of the gaps separating them; ridge on the inner side relatively slender, evenly bent, with slightly widened dorsal tip and with ventral half extending well onto the ventral portion of the LAP.
Material examined
NHMB M1124, NHMB M11225 and 3 dissociated LAPs from the late Oxfordian of Savigna, France, the type material of Hess (1966); GZG.INV.78805 (1 dissociated LAP) from sample S1 of Gale (2011), GZG.INV.78806 (2 dissociated LAPs) from sample S2a of Gale (2011) and GZG.INV.78807 (4 dissociated LAPs) from sample S2b of Gale (2011), all from the Bifurcatus Zone, late Oxfordian of Savigna, France; 2 dissociated LAPs from the Bifurcatus Zone of Guldental, Switzerland, the original material of Hess (1966).
Description
Relatively small dissociated LAPs; of thick, massive, strongly curved general aspect; more than twice higher than wide (proximal LAPs) to approximately 1.5 times higher than wide (median to distal LAPs); dorsal edge rounded; distal edge convex; proximal edge concave, generally with very weak, rounded protrusion; no spurs; ventral portion of the LAPs broad, weakly widened ventrally, relatively short, accounting for one-quarter of the total LAP height; outer surface with finely meshed stereom, devoid of conspicuous ornament elements. Five to six large, ear-shaped spine articulations freestanding on bulging distal portion of LAP and composed of a thick, continuous volute; spine articulations not sharply bordered proximally; weak dorsalward increase in size of spine articulations and slightly larger dorsalward increase in size of gaps separating them; gap between spine articulations and distal edge of LAP narrow.
Inner side of LAPs with well-defined, prominent, relatively slender, gently bent ridge; dorsal half of ridge pointing dorso-proximalwards, with slightly widened dorsal tip; ventral half of ridge extending onto most of the ventral portion of the LAP but not merged with the latter; no spurs on inner side of the distal edge of LAP; inner side of the tentacle notch moderately large, poorly defined, very shallow. Few, small, scattered perforations in shallow, moderately well-defined vertical furrow dorsally bordering tentacle notch.
Remarks
This type of LAP was originally described by Hess (1966) as Hemieuryale? lunaris on the basis of dissociated LAPs and vertebrae from the Oxfordian of Switzerland and France. A re-examination of the type material, in addition to new finds of dissociated LAPs from the Oxfordian of France, has now revealed that this LAP type displays the distinctive combination of characters unambiguously warranting assignment to Ophiojagtus gen. nov.
Occurrence
Late Oxfordian of France and Switzerland.
description: Published as part of 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), pp. 1-242 in European Journal of Taxonomy 48 on pages 215-216, DOI: 10.5852/ejt.2013.48, http://zenodo.org/record/3822836