Ophiolimna kucerai, 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 : 71-73

Ophiolimna kucerai sp. nov.

urn:lsid:zoobank.org:act:736B12D4-3C48-4CE3-A6B4-FA0B1CE9BDCE

Fig. 14 : 4-7

Diagnosis

Species of Ophiolimna with small LAPs; ventral third to quarter strongly protruding ventroproximalwards; up to five moderately large spine articulations; relatively wide gap between spine articulations and distal edge of LAP; inner side with nearly straight, oblique, spoon-shaped dorsal ridge displaying strongly widened, round dorsal tip, and second, ventral, much shorter, nearly straight, ventroproximally pointing ridge.

Etymology

Species named in honour of Michal Kucera for generously providing the samples yielding the type material of the species, and for the very fruitful and encouraging discussions on the potential of ophiuroids as a model to explore the evolutionary history of modern deep-sea benthos.

Type material

Holotype GZG.INV.78566 .

Paratypes

GZG.INV.78567, GZG.INV.78568 and GZG.INV.78569.

Type locality and horizon

Blake Nose, borehole ODP 171B 1049A 20x5, tropical northeast Atlantic; latest Aptian to earliest Albian, Hedbergella trochoidea to Microhedbergella rischi planktonic foraminifer zones, Early Cretaceous.

Additional material

GZG.INV.78568 (752 dissociated LAPs).

Description

Holotype

GZG.INV.78566 is a dissociated, small, proximal LAP; dorsal edge oblique, very weakly concave; distal edge irregularly undulose; proximal edge devoid of spurs, with large, slightly thickened, very poorly defined central part; ventral quarter strongly protruding ventro-proximalwards; outer surface with well-developed, coarse, regular vertical striation composed of broad, overlapping lamellae replaced by finely meshed stereom in very narrow band along proximal edge. Five moderately large, nearly equi-distant, ear-shaped spine articulations in relatively deep notches of weakly elevated distal edge of LAP; overlapped by the undulose distalmost lamella and connected with the latter by the moderately large, tongue-shaped ventral lobes of the spine articulations; dorsalward increase in the size of the spine articulations; gap between spine articulations and distal edge of LAP relatively wide. Ventral edge of LAP with moderately large, concave tentacle notch.

Inner side of LAP with sharply defined, prominent, very slender, relatively long, oblique, nearly straight, spoon-shaped dorsal ridge with strongly widened, round dorsal tip; second much shorter, slightly wider, ventro-proximalwards pointing ridge on ventral portion of LAP; inner side of distal edge of LAP devoid of spurs; inner side of tentacle notch moderately large. No perforations or furrow discernible.

Paratype supplements and variation

GZG.INV.78567 is a dissociated proximal LAP, ventro-proximal part strongly fragmentary; very well in agreement with holotype. Five spine articulations similar to those observed on holotype but slightly larger, with stronger dorsal increase in size, and with larger and thicker lip-shaped ventral lobe connected with the distalmost lamella.

GZG.INV.78568 is a dissociated median LAP; approximately 1.5 times wider than high; dorsal edge very weakly concave as a result of a slight constriction; vertical striation on outer surface less regular than in holotype and composed of finer lamellae. Four spine articulations similar to thos observed on holotype; dorsalmost and ventralmost spine articulations slightly smaller than remaining two.

Inner side of LAP with single ridge composed of oblique, near-straight dorsal part with very weakly widened dorsal tip, and much shorter, slightly wider ventral part; both parts of ridge connected by rounded kink.

GZG.INV.78569 is a dissociated distal LAP; more than twice wider than high. Three spine articulations similar to those observed on holotype.

Inner side largely obscured by sediment; slender, oblique, near-straight dorsal part of ridge discernible.

Remarks

These LAPs are unambiguously assignable to Ophiolimna on account of the highly distinctive spine articulation morphology and the outer surface striation. Within this genus, greatest similarities are shared with the LAPs of Ophiolimna malagasica sp. nov. (see above), which, however, are smaller and display six rather than five spine articulations separated by a much narrower gap from the distal edge of the LAP.

Occurrence

Latest Aptian to earliest Albian of the tropical northeast Atlantic.

Figures

Fig. 14. Fossil lateral arm plates (LAPs) of ophiacanthid brittle stars in external (a) and internal (b) views. 1-3. Ophiolimna lisae sp. nov. from the early Kimmeridgian of the Pointe du Chay (1), France, and the late Kimmeridgian of Trancoso, Portugal (2-3). 1. GZG.INV.78561 (holotype), proximal LAP. 2. GZG. INV.78562 (paratype), proximal LAP. 3. GZG.INV.78563 (paratype), median LAP. 4-7. Ophiolimna kucerai sp. nov. from the latest Aptian to earliest Albian (Early Cretaceous) of Blake Nose, NE Atlantic. 4. GZG.INV.78566 (holotype), proximal LAP. 5. GZG.INV.78567 (paratype), median LAP. 6. GZG. INV.78568 (paratype), distal LAP. 7. GZG.INV.78569 (paratype), proximal LAP. 8-10. Geromura touertensis gen. et sp. nov. from the Bajocian-Bathonian boundary of Touert, France. 8. GZG.INV.78571 (holotype) median to proximal LAP. 9. GZG.INV.78572 (paratype), proximal LAP. 10. GZG.INV.78573 (paratype), distal LAP. One common scale bar per species is given.