Ophiomalleus beneficarum, 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 : 182-184

Ophiomalleus beneficarum sp. nov.

urn:lsid:zoobank.org:act:7B911036-1E01-4EDA-AF2C-E56F0027B8F4

Fig. 32 : 3-6

Ophiacantha? constricta – Kutscher 1987a: 61, pl. 3 figs 1-2 (material incorrectly assigned to Ophiacantha? constricta Hess, 1966 ).

Diagnosis

Species of Ophiomalleus gen. nov. with very large LAPs displaying a poorly developed vertical striation on narrow band near spine articulations; at least six poorly defined spurs on proximal outer edge in proximal LAPs; up to five spine articulations with finely corrugated proximal edge and strong dorsalward increase in size except for often very small dorsalmost one; single, moderately broad, strongly prominent, S-shaped ridge on inner side.

Etymology

Name formed after beneficum, Latin for “charitable”, in reference to the infamous malleus maleficarum, to recall that witch hunts, regrettably, did not go extinct for good in the Dark Ages.

Type material

Holotype GZG.INV.78741 .

Paratype

GZG.INV.78742, GZG.INV.78743 Althütendorf, Germany; and GZG.INV.78744 Hohensaaten, Germany; all from glacial erratic boulders, Callovian, Middle Jurassic.

Type locality and horizon

Bauer-Wehrland, Germany; glacial erratic boulders, Callovian, Middle Jurassic.

Additional material

GZG.INV.78745 (18 dissociated LAPs) from the Callovian of Bauer-Wehrland, Germany; GZG. INV.78746 (5 dissociated LAPs) from the Callovian of Althüttendorf, Germany; GZG.INV.78747 (11 dissociated LAPs) from the Callovian of Hohensaaten, Germany.

Description

Holotype

GZG.INV.78741 is a dissociated, very large, proximal to median LAP; approximately 1.5 times higher than wide; main portion of LAP of rounded rectangular outline; dorsal and distal edges gently convex; proximal edge nearly straight, with four relatively small, poorly defined, almost indiscernible, horizontally elongate spurs; ventral portion of LAP very large, conspicuously protruding ventralwards; ventro-distal tip of LAP strongly protruding ventralwards, tongue shaped; outer surface of LAP with fine, rather irregular vertical striation composed of slender, non-overlapping lamellae, and restricted to distal third of outer surface bordering spine articulations; moderately finely meshed stereom on ventral portion of LAP and most of the median third of the outer surface; proximal third with very finely meshed and between spurs weakly horizontally striated stereom. Four very large, ear-shaped spine articulations freestanding on strongly elevated distal portion of LAP; very strong dorsalward increase in size of spine articulations and weaker dorsalward increase in size of gaps separating them; ventral and dorsal lobes of spine articulations merged into continuous volute; proximal edge of volute finely but irregularly corrugated; ventralmost spine articulation on protruding ventro-distal tip of LAP; dorsalmost spine articulation not at dorsal edge of LAP; row of spine articulations slightly oblique; gap between spine articulations and distal edge of LAP nearly as wide as half one spine articulation. Ventral edge of LAP nearly straight, with deeply incised, relatively small, more than semi-circular tentacle notch.

Inner side of LAP with large, moderately broad, strongly prominent, nearly S-shaped ridge, with ventral tip pointing ventro-proximalwards and confluent with ventral portion of LAP, and dorsal tip pointing dorsalwards and separated from dorsal edge of LAP; inner side of distal edge of LAP with two relatively large, well-defined, slightly prominent, horizontally elongate spurs. Three irregular perforations loosely arranged in vertical row dorsally bordering tentacle notch.

Paratype supplements and variation

GZG.INV.78742 is a dissociated proximal LAP; ventral portion missing; LAP originally more than 1.5 times higher than wide; main portion of LAP nearly rectangular to trapezoid in outline; dorsal edge irregularly convex; distal edge nearly straight; proximal edge gently concave, with at least six small to moderately large, poorly defined, horizontally slightly elongate, weakly prominent, nonprotruding spurs; outer surface with moderately finely meshed stereom; trabeculae of stereom near spine articulations thickened and merged into very poorly developed, irregular vertical striation. Five spine articulations similar to those of holotype; strong dorsalward increase in size of spine articulations except for very small dorsalmost one.

Dorsal half of ridge on inner side preserved, uniformly broad, well defined, strongly prominent, composed of straight, near-vertical dorsal portion and oblique, slightly bent central part; both parts connected by round kink; at least three spurs similar to those observed on holotype. Three very small, closely spaced perforations in very short vertical row dorsally bordering tentacle notch.

GZG.INV.78743 is a dissociated distal LAP; nearly as wide as high; very well in agreement with holotype; dorsal edge concave as a result of a constriction; proximal edge with three spurs similar to those of holotype; outer surface with moderately finely meshed stereom, no vertical striation. Three spine articulations similar to those of holotype, slightly smaller, in shallow notches of elevated distal edge of LAP and with better-developed fine corrugation on proximal edge of volute. Ventral edge of LAP slightly concave, with deeply incised slightly less than semi-circular tentacle notch.

Ridge on inner side of LAP similar to that of holotype except for a shorter, near-vertical dorsal portion of the ridge.

GZG.INV.78744 is a very large, cylindrical, slightly bulgy arm spine; tip broken, exposing hollow lumen; spine with moderately coarse, irregularly longitudinal trabecular ridges beset with minute granules.

Remarks

The specimens at hand were initially described and figured as Ophiacantha ? constricta Hess, 1965 by Kutscher (1987a) as a result of the misleading inclusion of more than one type of LAPs in the concept of that species. The LAP type including the holotype of O.? constricta, here transferred to Ophiogaleus gen. nov. (see above), however, fundamentally differs from the LAPs described above. The latter are here assigned to Ophiomalleus gen. nov., as discussed above. Within this genus, these LAPs are unique in displaying up to five spine articulations, a poorly developed vertical striation in median and, to a lesser extent, proximal LAPs, up to six poorly defined spurs on the outer proximal edge, and a moderately broad, S-shaped ridge on the inner side. Since the LAPs described above display the highly distinctive features of the new genus best it is chosen as its type species.

Occurrence

Callovian of Germany.

Figures

Fig. 32. Fossil skeletal plates of ophiacanthid brittle stars; lateral arm plates (LAPs) in external (a) and internal (b) views. 1. Ophiomitrella? sp. 2 from the Bathonian (Middle Jurassic) of Jumara, India; GZG. INV.78740, median to distal LAP. 2. Ophiomitrella sp. nov. from the late Maastrichtian (Late Cretaceous) of Maastricht, the Netherlands; NHMM JJ 5104, proximal LAP. 3-6. Ophiomalleus beneficarum gen. et sp. nov. from the Callovian of Bauer-Wehrland (3), Althüttendorf (4-5) and Hohensaaten (6), Germany. 3. GZG.INV.78741 (holotype), proximal to median LAP. 4. GZG.INV.78742 (paratype), proximal LAP. 5. GZG.INV.78743 (paratype), distal LAP. 6. GZG.INV.78744 (paratype), arm spine. 7-9. Ophiomalleus stevenwilsoni gen. et sp. nov. from the latest Hauterivian (Early Cretaceous) of Sarstedt, Germany. 7. GZG.INV.78748 (holotype), proximal LAP. 8. GZG.INV.78749 (paratype), median LAP. 9. GZG. INV.78750 (paratype), distal LAP. One common scale bar per species except for 6.