Ophiologimus martynovi, 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 : 51-53

Ophiologimus martynovi sp. nov.

urn:lsid:zoobank.org:act:F05FA7AB-4BE9-43BE-B1D1-693D08CAE2D2

Fig. 11 : 2-4

Diagnosis

Species of Ophiologimus with large LAPs; well-developed vertical striation composed of overlapping lamellae at least in proximal LAPs; up to three large, ear-shaped spine articulations; ventral lobe more slender than dorsal one and projecting ventro-distalwards beyond latter; inner side of LAP with moderately wide, straight, oblique ridge ventrally not merged with ventral portion of LAP; tentacle notch very deeply incised.

Etymology

Species named in honour of Alexander Martynov, who generously provided SEM pictures of lateral arm plates of Recent species of Ophiologimus for comparison.

Type material

Holotype GZG.INV.78532 .

Paratypes

GZG.INV.78533 and GZG.INV.78534.

Type locality and horizon

Blake Nose, borehole ODP 171B 1049C 12x6, tropical northeast Atlantic; latest Aptian to earliest Albian, Hedbergella trochoidea to Microhedbergella rischi planktonic foraminifer zones, Early Cretaceous.

Additional material

GZG.INV.78535 (45 dissociated LAPs).

Description of holotype

Holotype

GZG.INV.78532 is a dissociated, large proximal LAP; nearly as high as wide; dorso-proximal tip fragmentary; outline of dorsal edge not determinable; distal edge gently convex; proximal edge irregularly concave, devoid of spurs; ventral third of LAP strongly protruding ventro-proximalwards; ventro-distal tip of LAP strongly protruding ventralwards, tongue shaped; outer surface with well-developed, rather irregular, coarse vertical striation composed of overlapping lamellae with proximalward decrease in size and replaced by moderately coarsely to finely meshed stereom in proximal half of outer surface. Three large, equal-sized and equidistant, ear-shaped, nearly round spine articulations freestanding on non-elevated distal portion of LAP; dorsal and ventral lobes merged into continuous volute; ventral lobe more slender and smaller than dorsal one, ventro-distalwards projecting beyond dorsal lobe; gap between spine articulations and distal edge of LAP increasing in width ventralwards. Ventral edge of LAP with very large, deeply incised, concave tentacle notch.

Inner side of LAP with large, sharply defined, prominent, oblique, straight ridge with very weakly widened, round dorsal and ventral tips; no kinks, knobs or extensions; no spurs on inner side of distal edge of LAP; inner side of tentacle notch very large, with coarsely meshed, horizontally elongate stereom. No perforations or furrow discernible.

Paratype supplements and variation

GZG.INV.78533 is a dissociated median LAP; approximately 1.5 times higher than wide; closely similar to holotype; outer surface with coarsely meshed stereom, trabeculae not merged into vertical striation; coarsely meshed stereom replaced by more finely meshed stereom near proximal edge of LAP. Three spine articulations similar to those observed on holotype. Tentacle notch large and conspicuous but not as deep as in holotype. Ridge on inner side similar to that of holotype.

GZG.INV.78534 is a dissociated distal LAP; almost twice wider than high; dorsal edge slightly concave as a result of a weak constriction; outer surface with coarsely meshed stereom; few trabeculae merged into very weak, almost indiscernible vertical striation in distal half of outer surface; coarsely meshed stereom replaced by more finely meshed one towards proximal edge of LAP. Three spine articulations similar to those observed on holotype; ventral spine articulation slightly smaller than remaining two. Tentacle notch not as deep as in holotype but large, conspicuous, concave.

Ridge on inner side of LAP with strongly widened ventral tip; dorsal part of ridge straight, slender and oblique.

Remarks

These LAPs display the distinctive combination of characters typically found in LAPs of Ophiologimus , thus warranting assignment to this genus. Closest similarities are shared with the LAPs of Ophiologimus rugosus ( Kutscher & Jagt, 2000) comb. nov. (see below) in particular with respect to the outer surface vertical striation and the deeply incised tentacle notch. The LAPs of O. rugosus comb. nov., however, display up to seven, rather than three, spine articulations as well as two widely separate knobs or short ridges rather than a single large one on the inner side.

Occurrence

Latest Aptian to earliest Albian of the tropical northeast Atlantic.

Figures

Fig. 11. Lateral arm plates (LAPs) of fossil and Recent ophiacanthid brittle stars in external (a) and internal (b) views. 1. Ophiologimus hexactis H.L. Clark, 1911, Recent, median LAP in external view. 2-4. Ophiologimus martynovi sp. nov. from the latest Aptian to earliestAlbian (Early Cretaceous) of Blake Nose, NE Atlantic. 2. GZG.INV.78532 (holotype), proximal LAP. 3. GZG.INV.78533 (paratype), median LAP. 4. GZG.INV.78534 (paratype), distal LAP. 5-6. Ophiologimus aiodipius sp. nov. from the latest Aptian to earliest Albian (Early Cretaceous) of Blake Nose, NE Atlantic. 5. GZG.INV.78536 (holotype), proximal LAP. 6. GZG.INV.78537 (paratype), median LAP. 7-8. Ophiologimus rugosus (Kutscher & Jagt, 2000) comb. nov. from the early Maastrichtian (Late Cretaceous) of Rügen, Germany. 7. GZG. INV.78539, proximal LAP. 8. GZG.INV.78540, median LAP. One common scale bar per species is given.