Eolaxoporus, 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 : 25

Eolaxoporus sp. nov. innom.

Fig. 6 : 5

Material examined

GZG.INV.78500 (dissociated LAP) from the Cassian Formation, early Carnian of Milieres, Italy.

Description

GZG.INV.78500 is a dissociated, small, proximal to median LAP; slightly wider than high; dorsal and distal edges nearly straight; proximal edge gently concave except for very large, conspicuous, strongly protruding, moderately well-defined, prominent and slightly angular spur almost in the middle of the proximal edge and composed of slightly more densely meshed stereom; second much smaller and much less well defined, weakly prominent and non-protruding spur close to ventro-proximal edge of LAP; ventral fifth of LAP strongly protruding ventro-proximalwards; ventro-distal tip of LAP strongly protruding ventralwards, tongue-shaped; outer surface with moderately coarsely meshed stereom. Four moderately large, nearly equal-sized and equidistant spine articulations freestanding on slightly elevated distal portion of LAP; dorsal and ventral lobes of near-equal size, parallel, horizontal, widely separated proximally; gap between spine articulations and distal edge of LAP relatively narrow. Ventral edge of LAP with large, deeply incised, concave tentacle notch.

Inner side of LAP with very small, conspicuously slender, sharply defined, prominent, dorsoproximalwards bent ridge; two rather poorly defined, weakly prominent, round spurs on inner side of distal edge of LAP; inner side of tentacle notch very large. No perforations and furrow discernible.

Remarks

This single LAP displays all diagnostic characters of Eolaxoporus gen. nov. Within this genus, it is unique in having a strongly protruding, slightly angular dorsal spur almost in the centre of the proximal edge, and a very small, slender ridge on the inner side. The LAP in question certainly belongs to a new species which, in the absence of more material, cannot be described formally for now.

Figures

Fig. 6. Fossil lateral arm plates (LAPs) of ophiacanthid brittle stars in external (a) and internal (b) views. 1. Eolaxoporus sp. from the latest Anisian (Middle Triassic) of Oberscheffach, Germany, MHI 2083/1, median LAP. 2-4. Eolaxoporus hagdorni gen. et sp. nov. from the late Carnian (Late Triassic) of Jushui, China. 2. MHI 2084/1 (holotype), proximal LAP. 3. MHI 2085/1 (paratype), median LAP. 4. MHI 2086/1 (paratype), distal LAP. 5. Eolaxoporus sp. nov. innom. from the early Carnian (Late Triassic) of Milieres, Italy; GZG.INV.78500, proximal to median LAP. 6-8. Eolaxoporus imminens gen. et sp. nov. from the late Sinemurian to early Pliensbachian (Early Jurassic) of the Glasenbach Gorge, Austria. 6. NHMW 2012/0137/0001 (holotype), proximal LAP. 7. NHMW 2012/0137/0002 (paratype), median LAP. 8. NHMW 2012/0137/0003 (paratype), distal LAP. One common scale bar per species is given.