Lapidaster, 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 : 44

Lapidaster sp. nov. innom. 2

Fig. 10 : 4

Material examined

GZG.INV.78522 (dissociated LAP) from the Lacunosa Marls, early Kimmeridgian, Late Jurassic, of Geisingen, southern Germany.

Description

GZG.INV.78522 is a dissociated, small, proximal to median LAP; approximately 1.5 times wider than high; dorsal edge strongly concave as a result of a well-developed constriction; distal edge convex; proximal edge concave, with two well-defined, prominent spurs; ventral spur slender, strongly horizontally elongate, proximally pointed, non protruding; dorsal spur round, smaller, more strongly prominent, protruding; coarsely meshed stereom with thickened trabeculae on distal two-thirds of outer surface, replaced by finely meshed stereom on proximal third of outer surface. Three moderately large, equidistant, very poorly preserved spine articulations. Ventral edge of LAP with very large, but rather shallowly concave, tentacle notch.

Inner side of LAP with large, sharply defined, conspicuous, prominent ridge composed of straight, oblique dorsal half with non-thickened dorsal tip, and ventro-proximally bent, slightly broader ventral part; both parts of ridge connected by angular kink; one moderately large, well-defined, weakly prominent spur composed of densely meshed stereom on inner side of distal edge of LAP; second less well-defined, but larger and more prominent spur on inner side of ventro-distal tip of LAP; inner side of tentacle notch with coarsely meshed, horizontally elongate stereom. Single, moderately large perforation dorsally bordering tentacle notch.

Remarks

This LAP is strikingly similar to those of Lapidaster coreytaylori sp. nov. and L. mathcore sp. nov. with respect to general morphology, the outer surface stereom and the shape of the ridge on the inner side. It clearly belongs to the same group within Lapidaster gen. nov. as the two last-named species. The welldeveloped second spur on the outer proximal and inner distal edges sets the present LAP apart from those of Lapidaster coreytaylori sp. nov. and L. mathcore sp. nov. The LAP in question most probably represents a new species, the formal description and naming of which, however, cannot be based on a single, imperfectly preserved specimen.

Figures

Fig. 10. Fossil lateral arm plates (LAPs) of ophiacanthid brittle stars in external (a) and internal (b) views. 1-3. Lapidaster lukenederi gen. et sp. nov. from the late Valanginian (Early Cretaceous) of the Ternberg Nappe, Austria. 1. NHMW 2012/0138/0001 (holotype), proximal LAP. 2. NHMW 2012/0138/0002 (paratype), median LAP. 3. NHMW 2012/0138/0003 (paratype), distal LAP. 4. Lapidaster sp. nov. innom. 2 from the early Kimmeridgian (Late Jurassic) of Geisingen, Germany; GZG.INV.78522, proximal to median LAP. 5-7. Lapidaster coreytaylori gen. et sp. nov. from the middle Aptian (Early Cretaceous) of Carniol, France. 5. GZG.INV.78523 (holotype), proximal LAP. 6. GZG.INV.78524 (paratype), median LAP. 7. GZG.INV.78525 (paratype), distal LAP. 8-10. Lapidaster mathcore gen. et sp. nov. from the middle Albian (Early Cretaceous) of Folkestone, Great Britain. 8. GZG.INV.78528 (holotype), proximal LAP. 9. GZG.INV.78529 (paratype), median LAP. 10. GZG.INV.78530 (paratype), distal LAP. One common scale bar per species is given.