Dermocoma numbergerorum, 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 : 153-156

Dermocoma numbergerorum sp. nov.

urn:lsid:zoobank.org:act:EAD1DA00-C38B-49E3-B753-867F4C4DFA62

Fig. 28 : 1-4

Diagnosis

Species of Dermocoma with large LAPs displaying a well-developed, fine vertical striation on distal half of outer surface; ventral portion of proximal LAPs very large and wide; two large, nearly equalsized, strongly protruding, moderately well-defined and widely separate spurs on proximal outer edge of proximal LAPs: up to six large, nearly equal-sized spine articulations; dorsalward increase in gaps separating spine articulations; ridge on the inner side with long, slender, near-straight and oblique dorsal part with triangular, elongate, pointed dorsal tip.

Etymology

Species named in honour of Sabine and Klaus Numberger, the best in-laws of the Phanerozoic.

Type material

Holotype GZG.INV.78695 .

Paratypes

GZG.INV.78696, GZG.INV.78697 and GZG.INV.78698.

Type locality and horizon

Foug, France; marly pockets between coral bioherms, Transversarium Zone, middle Oxfordian, Late Jurassic.

Additional material

GZG.INV.78699 (201 dissociated LAPs).

Description

Holotype

GZG.INV.78695 is a dissociated, large, proximal LAP; 1.5 times higher than wide; dorsal edge nearly straight; distal edge slightly convex; ventral quarter of LAP very large, wide, strongly protruding ventroproximalwards; proximal edge irregularly undulose, with two large, almost equal-sized, moderately well-defined, prominent and conspicuously protruding, widely separate spurs; outer surface with very fine, regular vertical striation composed of slender, slightly overlapping lamellae, and replaced by very finely meshed stereom on the proximal two-thirds of the outer surface. Five large, nearly equal-sized, ear-shaped spine articulations in tight notches of elevated distal portion of LAP; ventral lobe merged with dorsal one into continuous volute, and connected with distalwards projecting tip of outer surface separating notch; spine articulations proximally sharply separated by edge of notch; dorsalward increase in size of gaps separating spine articulations; notches deeply incising vertical striation; moderately wide gap between spine articulations and distal edge of LAP. Ventral edge of LAP with moderately large, concave tentacle notch.

Inner side of LAP with large, sharply defined, prominent, slender ridge; ventral part of ridge gently bent ventro-proximalwards, not merged with weakly thickened ventral portion of LAP; dorsal part of ridge much longer than ventral one, nearly straight, oblique, with elongate, very slender triangular, pointed, approximately knife-shaped dorsal tip; inner side of distal edge with two moderately well-defined, widely separate, weakly prominent, oval spurs composed of more densely meshed stereom; ventral spur slightly smaller than dorsal one; inner side of tentacle notch moderately large, well defined laterally. Shallow, moderately well-defined vertical furrow dorsally bordering tentacle notch; no perforations discernible.

Paratypes

GZG.INV.78696 is a dissociated proximal LAP; very well in agreement with holotype; proximal edge and ventral portion slightly fragmentary; spurs on proximal edge as in holotype. Six spine articulations similar to those observed on holotype but less well preserved.

Inner side of LAP matching that of holotype. Vertical furrow with few small, scattered perforations.

GZG.INV.78697 is a dissociated median LAP; slightly higher than wide; proximal edge with two moderately well-developed, strongly prominent and protruding spurs; not as widely separated as in holotype, and dorsal spur slightly larger than ventral one; vertical striation on distal half rather than third of outer surface. Five spine articulations similar to those observed on holotype; dorsalward increase in size of gaps separating spine articulations stronger than in holotype; gap between spine articulations and distal edge of LAP narrower.

Inner side of LAP with ridge similar to that of holotype; spurs on inner side of distal LAP edge almost indiscernible. Two to three irregular, variably sized perforations dorsally bordering tentacle notch; no furrow discernible.

GZG.INV.78698 is a dissociated distal LAP; slightly wider than high; dorsal edge slightly concave as a result of a weak constriction; ventral portion of LAP weakly protruding ventro-proximalwards; spurs as in holotype; distal two-thirds of outer surface with vertical striation. Four spine articulations similar to those observed on holotype. Tentacle notch not visible in external view.

Inner side of LAP with sharply defined, slender, bent ridge; dorsal part of ridge dorso-proximally pointing, not thickened, with rounded tip; ventral part of ridge ventro-proximally pointing, with very weakly thickened ventral tip; inner side of tentacle notch relatively small, with coarsely meshed, horizontally elongate stereom, and sharply defined laterally. Very shallow, poorly defined vertical furrow dorsally bordering tentacle notch.

Remarks

Assignment of these LAPs to Dermocoma is corroborated by the strongly ventro-proximally protruding ventral portion of the LAPs, the shape and position of the spine articulations and the shape of the ridge on the inner side. Within this genus, the present LAPs are unique in combining up to six spine articulations, two well-defined, widely separate spurs on the outer proximal and inner distal edges, and a conspicuously large and wide ventral portion. They are thus described here as a new species of Dermocoma .

Figures

Fig. 28. Fossil lateral arm plates (LAPs) of ophiacanthid brittle stars in external (a) and internal (b) views. 1-4. Dermocoma numbergerorum sp. nov. from the middle Oxfordian (Late Jurassic) of Foug, France. 1. GZG.INV.78695 (holotype), proximal LAP. 2. GZG.INV.78696 (paratype), proximal LAP. 3. GZG.INV.78697 (paratype), median LAP. 4. GZG.INV.78698 (paratype), distal LAP. 5-8. Dermocoma simonschneideri sp. nov. from the early Kimmeridgian (Late Jurassic) of the Pointe du Chay, France (5) and the late Kimmeridgian (Late Jurassic) of Trancoso, Portugal (6-8). 5. GZG.INV.78700 (holotype), proximal LAP. 6. GZG.INV.78701 (paratype), proximal LAP. 7. GZG.INV.78702 (paratype), median LAP. 8. GZG. INV.78703 (paratype), distal LAP. 9. Dermocoma sp. nov. innom. 2 from the early Kimmeridgian (Late Jurassic) of Geisingen, Germany; GZG.INV.78705, median to distal LAP.10-11. Dermocoma sp. nov.innom. 3 from the late Valanginian (Early Cretaceous) of the Ternberg Nappe, Austria. 10. NHMW 2012/0138/0009, proximal LAP. 11. NHMW 2012/0138/0010, distal LAP. One common scale bar per species.