Ophiojagtus, 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 : 220-221

Ophiojagtus sp. indet.

Fig. 38 : 8

Material examined

GZG.INV.78818 (1 dissociated LAP) from the early Cenomanian, Late Cretaceous of Waco, Texas, USA.

Description

GZG.INV.78818 is a dissociated, moderately large, proximal LAP; ventral portion and dorso-proximal edge missing; distal edge convex; proximal edge with very large, conspicuous, well-developed protrusion; outer surface with finely meshed stereom. Five large, ear-shaped spine articulations freestanding on strongly bulging distal portion of LAP and composed of a thick, continuous volute; dorsalward increase in the size of the spine articulations and of the gaps separating them; gap between the spine articulations and the distal edge of the LAP narrow.

Inner side of the LAP with moderately well-defined, weakly prominent, broad ridge with conspicuous, strongly widened dorsal tip extending ventro-proximalwards on inner side of protrusion of proximal LAP edge; presence of a ventral part of the ridge not determinable. Single small perforation at the ventral tip of a shallow, poorly defined vertical furrow distally bordering the ventralmost preserved part of the ridge.

Remarks

Although the single LAP described above is unambiguously assignable to Ophiojagtus gen. nov., its fragmentary nature precludes any species-level identification. The presence of five spine articulations places this LAP closest to O. acklesi sp. nov. or to the LAPs described by Štorc & Žítt (2008) and probably erroneously assigned to O. alternatus comb. nov. (see below). However, since the ventral portion is missing, the shape of the ridge on the inner side cannot be assessed, which precludes any further conclusions on the placement of the specimen at the species level.

Figures

Fig. 38. Fossil lateral arm plates (LAPs) of ophiacanthid brittle stars in external (a) and internal (b) views. 1-4. Ophiojagtus irimurai gen. et sp. nov. from the early Kimmeridgian (Late Jurassic) of the Pointe du Chay, France. 1. GZG.INV.78808 (holotype), proximal LAP. 2. GZG.INV.78809 (paratype), median LAP. 3. GZG.INV.78810 (paratype), median LAP. 4. GZG.INV.78811 (paratype), distal LAP. 5-7. Ophiojagtus acklesi gen. et sp. nov. from the late Aptian (Early Cretaceous) of Wizard Way, Texas. 5. GZG.INV.78814 (holotype), proximal LAP. 6. GZG.INV.78815 (paratype), median to distal LAP. 7. GZG.INV.78816 (paratype), proximal LAP. 8. Ophiojagtus sp. 1 from the early Cenomanian (Late Cretaceous) of Waco, Texas; proximal LAP. 9-10. Ophiojagtus alternatus (Kutscher & Jagt, 2000) comb. nov. from the early late Maastrichtian (Late Cretaceous) of Haccourt, Belgium. 9. NHMM 2012 060, proximal to median LAP. 10. NHMM 2012 061, proximal LAP. One common scale bar per species.