Lapidaster wolfii, 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 : 36-37

Lapidaster wolfii sp. nov.

urn:lsid:zoobank.org:act:ECF21B65-FAD1-488C-8343-0C5C3E192B74

Fig. 8 : 2-4

Diagnosis

Species of Lapidaster gen. nov. with moderately large LAPs showing coarsely meshed stereom with trabecular merging into a very weak vertical striation; up to six large, equal-sized spine articulations.

Etymology

Species named in honour of my friend and former band-mate Wolfgang (“Wolfi”) Prebeck, for cheering up moments of frustration, in particular during the course of the present study.

Type material

Holotype GZG.INV.78508 .

Paratypes

GZG.INV.78509 and GZG.INV.78510.

Type locality and horizon

Touert near Chaudon, France; marl bed at the Bajocian-Bathonian boundary, Middle Jurassic.

Description

Holotype

GZG.INV.78508 is a dissociated, small, proximal lateral arm plate, slightly higher than wide, of irregularly angular aspect; ventral quarter of LAP protruding ventro-proximalwards; ventro-distal tip of LAP slightly protruding; dorsal and distal edges of LAP nearly straight; proximal edge slightly undulose, with very faint, almost indiscernible spur close to ventro-proximal tip. Outer surface with coarsely reticulate stereom with trabeculae tending to merge into a very faint, irregular vertical ridges, rapidly grading into finely meshed stereom close to distal edge of LAP; reticulate stereom separated from three ventral spine articulations, and slightly confluent with proximal edge of three dorsalmost spine articulations. Six, large, ear-shaped spine articulations with dorsal and ventral lobes forming a continuous volute, freestanding in continuous vertical row close to distal edge of LAP, equal in size but with slight dorsalward increase in size of gaps separating them. Ventral edge of LAP with large, concave tentacle notch.

Inner side of LAP with single relatively thin, sharply defined, prominent, oblique ridge, of nearly constant width and with rounded dorsal tip: dorsal half of ridge slightly bent dorsalwards; ventral half separated from dorsal one by rounded kink and confluent with thickened ventro-proximal edge of LAP. No perforations discernible. Inner distal edge thinning distalwards; ventro-distal tip thickened into an irregular, oblique, poorly defined, prominent spur. Inner side of tentacle notch with coarsely reticulate stereom, slightly stretched horizontally.

Paratype supplements and variation

GZG.INV.78509 is a dissociated median lateral arm plate, slightly higher than wide. Overall morphology well in agreement with that of holotype. Proximal edge of LAP strongly undulose, with large, relatively well-defined, slightly prominent spur on ventro-proximal tip, composed of denser stereom. Striation on outer surface slightly better developed than in holotype. A total of five spine articulations of equal size, poorly preserved, with slight increase in size of the gaps separating them.

Morphology of inner side of LAP as in holotype. Ventro-distal spur more clearly defined and slightly more prominent than in holotype.

GZG.INV.78510 is a dissociated distal lateral arm plate, wider than long, of rounded triangular aspect, with slightly convex dorsal and distal edges, and slightly undulose proximal edge; ventral quarter slightly protruding ventro-proximalwards; outer surface with coarsely reticulate stereom, with trabeculae showing hardly any tendency to develop into vertical striation; ventro-proximal tip of LAP poorly preserved. Three spine articulations of equal size, gap between dorsal and median spine articulation slightly larger than gap between median and ventral ones.

Morphology of inner side well in agreement with holotype and other paratype. Oblique ventro-distal spur large, sharply defined and strongly prominent, suggesting equally well-developed counterpart on outer ventro-proximal edge not observable due to insufficient preservation of the LAP. Tentacle notch large and conspicuous.

Remarks

The present species most closely resembles Lapidaster hystricarboris sp. nov. from which it differs, however, in displaying a much coarser and less well-developed vertical striation on the outer surface of the LAPs, as well as a slightly smaller dorsalward increase in the size of the gaps separating the spine articulations. It is thus described here as a new species. Assignment to Lapidaster gen. nov. is based on the strikingly Ophiologimus -like LAP morphology and the presence of a spur, albeit weakly developed, on the outer proximal and inner distal edges of the LAPs.

Occurrence

Bajocian-Bathonian boundary beds of France.

Figures

Fig. 8. Fossil lateral arm plates (LAPs) of ophiacanthid brittle stars in external (a) and internal (b) views. 1. Lapidaster sp. nov. innom. 1 from the late Toarcian (Early Jurassic) of Seewen, Switzerland; NHMB M11208, proximal to median LAP. 2-4. Lapidaster wolfii gen. et sp. nov. from the Bajocian-Bathonian boundary (Middle Jurassic) of Touert, France. 2. GZG.INV.78508 (holotype), proximal LAP. 3. GZG. INV.78509 (paratype), median LAP. 4. GZG.INV.78510 (paratype), distal LAP. 5-7. Lapidaster varuna gen. et sp. nov. from the Callovian of Jumara, India. 5. GZG.INV.78511 (holotype), proximal LAP. 6. GZG.INV.78512 (paratype), median LAP. 7. GZG.INV.78513 (paratype), distal LAP. One common scale bar per species is given.