Dermocoma, Hess, 1964

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 : 159

Dermocoma sp. nov. innom. 3

Fig. 28 : 10-11

Material examined

NHMW 2012/0138/0009, NHMW 2012/0138/0010 and NHMW 2012/0138/0011 (25 dissociated LAPs) from the Verrucosum Zone, late Valanginian of the KB1-A section of Lukeneder (2004), Ternberg Nappe, Austria.

Description

Dissociated, small, fragile, fragmentary proximal to median LAPs and a single complete distal LAP; proximal ones originally as high as wide or slightly higher; median ones slightly wider than high; distal LAP more than twice wider than high; dorsal edge concave in median to distal LAPs as a result of a weak constriction; distal edge convex; proximal edge of distal LAP with two small, poorly defined, slightly prominent and protruding spurs; no spurs discernible in fragmentary proximal edge of median to distal LAPs; ventral portion of median to proximal LAP fragmentary, originally most probably protruding; outer surface with very fine, irregular, slightly wavy vertical striation composed of very slender, slightly overlapping lamellae, and replaced by finely meshed stereom on proximal three-quarters of outer surface. Three rather small, ear-shaped spine articulations in notches of weakly elevated distal portion of LAP; possibly more spine articulations in proximal LAP; weak dorsalward increase in size of spine articulations in proximal LAP; ventral lobe of spine articulations not connected with outer surface stereom and merged with dorsal lobe into continuous volute; spine articulations proximally bordered by edge of notches; gap between spine articulations and distal edge of LAP narrow. Small, weakly concave tentacle notch in median LAPs; ventral edge of distal LAP evenly concave, tentacle opening emerging at ventro-distal edge of ventralmost spine articulation.

Inner side of proximal to median LAPs with sharply defined, prominent, very slender, slightly bent, oblique ridge dorsal tip of which pointing dorso-proximalwards and ventral tip pointing ventroproximalwards; two widely separate, sharply defined, prominent knobs on inner side of distal LAP, proximal one nearly triangular, distal one minute, almost indiscernible; inner side of distal edge of LAP with up to two poorly to moderately well-defined, small, oval, slightly prominent spurs; inner side of tentacle notch not preserved in proximal LAP, moderately large, well-defined laterally and with coarsely meshed, horizontally elongate stereom in median LAP; distal LAP with large tentacle perforation in the middle of the distal third. Two small, irregular perforations loosely arranged in vertical row on inner side of proximal LAP fragment.

Remarks

This material is very limited and largely fragmentary; yet, the shape and position of the spine articulations, the spurs on the outer proximal and inner distal edges and the shape of the ridge on the inner side strongly suggest assignment to Dermocoma . The fragmentary nature precludes assignment at the species level. Nevertheless, the material is very important since it was recovered from deep shelf to upper slope sediments and thus represents the deepest occurrence of Dermocoma recorded to date.

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.