Geromura teckliformis, 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 : 75-78

Geromura teckliformis sp. nov.

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Fig. 15 : 1-3

Diagnosis

Species of Geromura with moderately large LAPs, at least 3.5 times wider than high; two poorly defined and non-protruding spurs on the outer proximal edge paralleled by very weakly developed spurs composed of slightly more densely meshed stereom on the inner distal edge; up to five spine articulations; two widely separate knobs on inner side of all LAPs.

Etymology

Name derived from “Teckel”, the German sausage dog, in reference to the extremely elongate LAPs of the species.

Type material

Holotype

NHMW 2012/0138/0005 .

Paratypes

NHMW 2012/0138/0006 and NHMW 2012/0138/0007.

Type locality and horizon

KB1-A section of Lukeneder (2004) in the Ternberg Nappe, Austria; Verrucosum Zone, late Valanginian, Early Cretaceous.

Additional material

NHMW 2012/0138/0008 (123 dissociated LAPs).

Description

Holotype

NHMW 2012/0138/0005 is a dissociated, medium-sized, proximal LAP; rod shaped, approximately 3.5 times wider than high; dorsal edge concave as a result of a well-developed constriction; distal edge nearly straight; ventro-distal tip of LAP strongly protruding, tongue shaped; proximal edge irregularly concave, with two small, poorly defined, horizontally elongate, slightly prominent but not protruding spurs composed of slightly more densely meshed stereom; outer surface with very coarsely meshed stereom, replaced by finely meshed stereom in a narrow band along the proximal edge of the LAP; intersections of trabeculae not thickened into granules. Five small, round to slightly ear-shaped, equidistant spine articulations of rugged appearance, freestanding on elevated distal portion of LAP; ventralmost spine articulation slightly smaller than remaining four; dorsalmost spine articulation on dorsal edge of LAP, hardly discernible in external view; ventral and dorsal lobes of spine articulations forming nearly circular volute with very small sigmoidal fold and very small nerve opening; gap between spine articulations and distal edge of LAP very wide, almost twice wider than spine articulations. Ventral edge of LAP gently convex except for very large, concave tentacle notch.

Inner side of LAP with two very small, sharply defined, prominent, round and widely separate knobs composed of finely meshed stereom; inner side of distal edge of LAP with two very weakly defined, non-prominent and non-protruding spurs composed of slightly more densely meshed stereom. No perforations discernible.

Paratype supplements and variation

NHMW 2012/0138/0006 is a dissociated median LAP; four times wider than high; spurs on proximal edge very small, hardly discernible. Four spine articulations, ventralmost slightly smaller than remaining three; gap separating spine articulations and distal edge of LAP more than twice wider than spine articulations. Ventral edge of LAP nearly straight, with very large concave tentacle notch.

Inner side of LAP well in agreement with that of holotype.

NHMW 2012/0138/0007 is a dissociated distal LAP; five times wider than high; spurs on proximal edge very small, hardly discernible. Three poorly preserved spine articulations; row of spine articulations strongly protruding dorsalwards; gap between spine articulations and distal edge of LAP wider than

one spine articulation. Ventral edge of LAP very gently concave, no tentacle notch; hardly discernible tentacle opening near ventro-distal edge of ventralmost spine articulation.

Inner side of LAP obscured by sediment.

Remarks

Differences between the present LAPs and Geromura touertensis sp. nov. are discussed above. The present LAPs are so highly distinctive that there is hardly any chance to confuse them with any other ophiuroid species.

Occurrence

Late Valanginian of Austria.

Figures

Fig. 15. Fossil lateral arm plates (LAPs) of ophiacanthid brittle stars in external (a) and internal (b) views. 1-3. Geromura teckliformis gen. et sp. nov. from the late Valanginian (Early Cretaceous) of the Ternberg Nappe, Austria. 1. NHMW 2012/0138/0005 (holotype), proximal LAP. 2. NHMW 2012/0138/0006 (paratype), median LAP. 3. NHMW 2012/0138/0007 (paratype), distal LAP. 4-6. Krohcoma mira gen. et sp. nov. from the late Sinemurian to early Pliensbachian (Early Jurassic) of the Glasenbach Gorge, Austria. 4. NHMW 2012/0137/0013 (holotype), proximal LAP. 5. NHMW 2012/0137/0014 (paratype), median LAP. 6. NHMW 2012/0137/0015 (paratype), distal LAP. 7-8. Krohcoma sp. nov. innom from the late Bathonian (Middle Jurassic) of Jumara, India. 7. GZG.INV.78574, proximal LAP. 8. GZG.INV.78575, median to distal LAP. 9-12. Krohcoma ampla gen. et sp. nov. from the early Kimmeridgian of the Pointe du Chay (9-10), France, and the late Kimmeridgian of Trancoso, Portugal (11-12). 9. GZG.INV.78577 (holotype), proximal LAP. 10. GZG.INV.78578 (paratype), median LAP. 11. GZG.INV.78579 (paratype), median LAP. 12. GZG.INV.78580 (paratype), distal LAP. One common scale bar per species is given.