Lapidaster mathcore, 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 : 49-51

Lapidaster mathcore sp. nov.

urn:lsid:zoobank.org:act:134870A5-8900-4C8F-97E4-8D098266865D

Fig. 10 : 8-10

Diagnosis

Species of Lapidaster gen. nov. with moderately large LAPs with coarsely meshed stereom in a narrow band of the outer surface displaying conspicuously thick trabeculae; ventral portion very narrow and strongly protruding ventro-proximalwards; spur on outer proximal edge oval, slightly horizontally elongate, not pointed proximally, paralleled by a well-defined spur on the inner distal edge; dorsal part of ridge on the inner side bent proximally.

Etymology

Species named after “Mathcore”, a music genre that has been among my most influential sources of inspiration in understanding and expressing complexity.

Type material

Holotype GZG.INV.78528 .

Paratypes

GZG.INV.78529 and GZG.INV.78530.

Type locality and horizon

Folkestone, Great Britain; level 2 of Young et al. (2010), Loricatus Zone , middle Albian, Early Cretaceous.

Additional material

GZG.INV.78531 (5 dissociated LAPs).

Description

Holotype

GZG.INV.78528 is a dissociated, moderately large, proximal LAP; nearly 1.5 times wider than high; distal edge convex; dorsal edge slightly concave as a result of a weakly developed constriction; ventral quarter of LAP very narrow, strongly protruding ventro-proximalwards; ventro-distal tip of LAP very large, tongue shaped and conspicuously protruding; proximal edge separated by sharp kink into dorsal and ventral portion; large, conspicuous, sharply defined, prominent and slightly elongated, oval spur composed of more densely meshed stereom at some distance from kink separating proximal edge; coarsely meshed stereom in distal half of outer surface; trabeculae of outer surface stereom thick, no tendency to merge into vertical striation; coarsely meshed stereom of outer surface replaced by more finely meshed stereom in proximal half of outer surface. Four ear-shaped spine articulations, with slight dorsalward increase in size of gaps separating them; second dorsalmost spine articulation slightly larger than remaining three; dorsal and ventral lobes forming continuous volute; all four spine articulations surrounded by irregular, confluent areoles of finely meshed stereom. Ventral edge of LAP with extremely large, deeply concave tentacle notch.

Inner side of LAP with large ridge separated by kink into sharply defined dorsal and less well-defined ventral portions; dorsal portion oblique, bent proximally, with weakly widened dorsal tip; ventral portion straight, forming a slightly obtuse angle with dorsal portion and approximately as long as the latter, with slightly thickened ventral tip not confluent with ventral portion of LAP; inner side of ventro-distal tip of LAP thickened with moderately well-defined, round, slightly prominent spur composed of dense stereom. Inner side of large tentacle notch with coarsely meshed and slightly horizontally stretched stereom dorsally bordered by large, irregular perforation.

Paratype supplements and variation

GZG.INV.78529 is a dissociated median LAP; well in agreement with holotype but slightly less well preserved; ventral portion of LAP smaller, slightly less strongly protruding ventro-proximalwards; proximal edge with spur on ventral portion similar to that observed on holotype; second much smaller, but similarly well-defined, spur in dorsal half of proximal edge. Three spine articulations similar to those observed on holotype. Tentacle notch very large but not as deeply concave as in holotype.

Ridge on inner side poorly preserved but superficially similar to that of holotype.

GZG.INV.78530 is a dissociated distal LAP; less well preserved than holotype; large spur in the middle of the ventral portion of the LAP probably similar to that of holotype; second small, slightly protruding, very poorly preserved spur in dorsal half of proximal edge; coarsely meshed stereom on distal twothirds of outer surface, replaced by finely meshed stereom on proximal third of outer surface. Three very poorly preserved spine articulations. Tentacle notch very large and almost as deeply incised as in holotype.

Ridge on inner side similar to that of holotype but with straight dorsal half and very poorly defined ventral half.

Remarks

These LAPs are remarkably similar to those of Lapidaster coreytaylori sp. nov. from slightly older deep-sea sediments in France. They can be unambiguously distinguished from the latter on account of the size of the ventral LAP portion, the extent of the coarsely meshed stereom on the outer surface, the shape and position of the spur on the ventral portion of the outer proximal edge, and the shape of the ridge on the inner side.

Occurrence

Middle Albian of Great Britain.

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.