Inexpectacantha acrobatica Thuy, 2011

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 : 192-193

Inexpectacantha acrobatica Thuy, 2011

Fig. 33 : 9-10

Inexpectacantha acrobatica Thuy, 2011: 217 , pls 1-3, pl. 4 figs 1-6.

Inexpectacantha acrobatica – Thuy et al. 2011: 179, fig. 3f.

Diagnosis

Species of Inexpectacantha with small LAPs; relatively small height/width ratio; outer surface with moderately coarsely meshed stereom and slight constriction resulting in concave dorsal edge and shallow, poorly defined furrow parallel to proximal edge; up to six moderately large, ear-shaped, oblique spine articulations freestanding on strongly bulging distal portion of LAP; ridge on inner side of LAP moderately broad and strongly bent dorso-proximalwards; two ventralmost spine articulations of distal LAPs with conspicuous, strongly prominent, lip-shaped distal ridges originally supporting hook-shaped arm spines.

Material examined

GZG.INV.78755 and GZG.INV.78756 (dissociated LAP) from the early Pliensbachian of Blockley, Great Britain; GZG.INV.78757 and GZG.INV.78758 (70 dissociated LAPs) from the early Toarcian of Aix-sur-Cloie, Belgium; the type material of Thuy (2011).

Remarks

The LAPs of Inexpectacantha acrobatica were described in detail and illustrated by Thuy (2011). The LAP morphological diagnosis presented above allows for an unambiguous distinction from other species of Inexpectacantha , including those known exclusively from dissociated LAPs. Two additional occurrences of the species are listed here, one of which extends the stratigraphic range into the early Toarcian.

Occurrence

Early Pliensbachian of France and Great Britain, early Toarcian of Belgium.

Figures

Fig. 33. Fossil lateral arm plates (LAPs) of ophiacanthid brittle stars in external (a) and internal (b) views. 1-3. Inexpectacantha ritae sp. nov. from the Hettangian (Early Jurassic) of Bourglinster, Luxembourg. 1. MnhnL HE419 (holotype), proximal LAP. 2. MnhnL HE420 (paratype), median LAP. 3. MnhnL HE421 (paratype), distal LAP. 4-6. Inexpectacantha weisi sp. nov. from the Hettangian (Early Jurassic) of Fontenoille, Belgium. 4. MnhnL HE425 (holotype), proximal LAP. 5. MnhnL HE426 (paratype), median LAP. 6. MnhnL HE427 (paratype), distal LAP. 7-8. Inexpectacantha lunaris (Hess, 1962) comb. nov. from the late Sinemurian (Early Jurassic) of Bishop’s Cleeve, Great Britain. 7. GZG. INV.78752, proximal LAP. 8. GZG.INV.78753, proximal to median LAP. 9-10. Inexpectacantha acrobatica Thuy, 2011 from the early Pliensbachian (Early Jurassic) of Blockley, Great Britain (9) and the early Toarcian (Early Jurassic) of Aix-sur-Cloie, Belgium (10). 9. GZG.INV.78755, proximal LAP. 10. GZG.INV.78757, juvenile proximal LAP. One common scale bar per species.