Dermacantha pattyana, 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 : 162-164

Dermacantha pattyana sp. nov.

urn:lsid:zoobank.org:act:4F9EF5AE-AF42-4815-B870-EF9964CEAEC8

Fig. 29 : 2-5

Diagnosis

Species of Dermacantha gen. nov. with small LAPs displaying a very finely meshed stereom on the outer surface; trabeculae of outer surface stereom merging into very poorly developed, irregular vertical striation close to spine articulations; two very weakly defined spurs on the outer proximal and inner distal edges; up to four relatively small spine articulations; ridge on inner side relatively short and wide.

Etymology

Species named in honour of my friend and near-sister Patty Muller.

Type material

Holotype

MnhnL HE414 .

Paratypes

MnhnL HE415, MnhnL HE416 and MnhnL HE417.

Type locality and horizon

Fontenoille, Belgium; level c of Delsate et al. (2002), Liasicus Zone, Hettangian, Early Jurassic.

Additional material

MnhnL HE418 (294 dissociated LAPs).

Description

Holotype

MnhnL HE414 is a dissociated, small,proximal to median LAP; nearly as high as wide;dorsal edge straight; distal edge convex; proximal edge irregularly concave, with two large, poorly defined, horizontally elongate and weakly prominent spurs, ventral one slightly larger and more strongly protruding; ventral sixth of LAP slightly protruding ventro-proximalwards; outer surface with very finely meshed stereom; trabeculae of outer surface stereom merging into very faint, poorly developed, irregular vertical striation close to spine articulations. Four relatively small, ear-shaped spine articulations sunken individually into moderately deep notches of the non-elevated distal LAP edge; ventral and dorsal lobes thin, separated by small knob proximally; spine articulations equal-sized and equi-distant; gap between spine articulations and distal edge of LAP moderately wide, slightly narrower than the width of one spine articulation, decreasing in width ventralwards. Ventral edge of LAP with small, concave tentacle notch.

Inner side of LAP with well-defined, prominent, relatively broad, short ridge; dorsal tip of ridge slightly widened, tongue shaped, pointing dorso-proximalwards; ventral part of ridge merged with thickened ventral LAP portion; inner side of distal edge with two medium-sized, poorly defined, oval, weakly prominent spurs; inner side of ventro-distal tip of LAP thickened; inner side of tentacle notch moderately large, sharply defined laterally. No perforations or furrow discernible.

Paratype supplements and variation

MnhnL HE415 is a dissociated proximal LAP; ventral portion missing; LAP originally higher than wide; generally well in agreement with holotype; dorsal edge oblique, slightly convex; two spurs on proximal edge very weakly defined; ventro-distal tip of LAP strongly protruding ventro-distalwards, tongue shaped; trabeculae of very finely meshed stereom on outer surface not merging into vertical striation. Four spine articulations similar to those observed on holotype.

Ridge on inner side of LAP slightly narrower and longer than that of holotype, almost vertical dorsally.

MnhnL HE416 is a dissociated median LAP; slightly higher than wide; spurs on outer proximal edge very poorly defined; ventro-distal tip of LAP very slightly protruding ventro-distalwards, rounded; trabeculae of outer surface stereom more commonly merging into vertical striation than in holotype; vertical striation better developed and more widespread rather than restricted to a very narrow band near the spine articulations. Four spine articulations similar to those observed in holotype; gap between spine articulations and distal edge of LAP narrower than in holotype; ventralmost spine articulation smaller than remaining three.

Inner side of LAP similar to that of holotype.

MnhnL HE417 is a dissociated distal LAP; approximately 1.5 times wider than high; poorly preserved; dorsal edge very slightly concave; spurs on proximal edge very poorly defined, almost indiscernible; only very few trabeculae of finely meshed outer surface stereom merged into poorly developed vertical striation. Two poorly preserved spine articulations apparently similar to those observed on holotype. Ventral edge of LAP nearly straight, with small, weakly concave tentacle notch.

Inner side with small, well-defined, nearly triangular, oblique ridge, with dorso-proximally pointing dorsal tip; ventral part widest, not merged with ventral portion of LAP; spurs on inner side of distal edge of LAP almost indiscernible.

Remarks

These LAPs are unambiguously assignable to Dermacantha gen. nov. on account of the general Dermocoma -like morphology with smaller spine articulations displaying a discontinuous volute. Greatest similarities are shared with the LAPs of Dermacantha seeweni comb. nov., which, however,

display a better-developed vertical striation on the outer surface, only one poorly defined spur, and up to five spine articulations with a conspicuously distalwards projecting ventral lobe.

Occurrence

Hettangian of Belgium.

Figures

Fig. 29. Fossil lateral arm plates (LAPs) of ophiacanthid brittle stars in external (a) and internal (b) views. 1. Dermocoma sp. nov. innom. 4 from the early Albian (Early Cretaceous) of Leighton Buzzard, Great Britain; NHM EE 14844, proximal LAP. 2-5. Dermacantha pattyana gen. et sp. nov. from the Hettangian (Early Jurassic) of Fontenoille, Belgium. 2. MnhnL HE414 (holotype), proximal LAP. 3. MnhnL HE415 (paratype), proximal LAP. 4. MnhnL HE416 (paratype), median LAP. 5. MnhnL HE417 (paratype), distal LAP. 6-8. Dermacantha seeweni (Kutscher & Hary, 1991) comb. nov. from the late Sinemurian (Early Jurassic) of Bishop’s Cleeve, Great Britain. 6. GZG.INV.78706, proximal LAP. 7. GZG.INV.78707, median LAP. 8. GZG.INV.78708, distal LAP. 9-11. Dermacantha leonorae gen. et sp. nov. from the early Pliensbachian (Early Jurassic) of Blockley, Great Britain. 9. GZG.INV.78710 (holotype), proximal LAP. 10. GZG.INV.78711 (paratype), median LAP. 11. GZG.INV.78712 (paratype), distal LAP. One common scale bar per species.