Ophiologimus aiodipius, 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 : 54-55

Ophiologimus aiodipius sp. nov.

urn:lsid:zoobank.org:act:C014CC2C-60E3-43F6-B1D6-20F6410E6A97

Fig. 11 : 5-6

Diagnosis

Species of Ophiologimus with large LAPs displaying coarsely meshed stereom on outer surface; trabeculae of coarsely meshed stereom merged into short, irregular vertical stripes close to spine articulations; up to four lenticular, oblique spine articulations; ridge on inner side of LAPs very slender; ventral part of ridge merged with ventral portion of LAP and connected with dorsal part of ridge by gently rounded kink; tentacle notch rather shallow.

Etymology

Species name derived from IODP, Integrated Ocean Drilling Program, under which the samples yielding the type material were recovered.

Type material

Holotype GZG.INV.78536 .

Paratypes

GZG.INV.78537.

Type locality and horizon

Blake Nose, borehole ODP 171B 1049C 12x5, tropical northeast Atlantic; latest Aptian to earliest Albian, Hedbergella trochoidea to Microhedbergella rischi planktonic foraminifer zones, Early Cretaceous.

Additional material

GZG.INV.78538 (33 dissociated LAPs).

Description

Holotype

GZG.INV.78536 is a dissociated, large, proximal LAP; slightly wider than high; dorsal edge straight; distal edge convex; proximal edge concave, devoid of spurs; ventral fifth of LAP strongly protruding ventro-proximalwards; ventro-distal tip of LAP slightly protruding; outer surface with coarsely meshed stereom; trabeculae merging into short, irregular, vertical stripes close to spine articulations; coarsely meshed stereom replaced by finely meshed stereom in narrow band along proximal edge of LAP. Four large, lenticular, oblique, slightly elongate, nearly equal-sized and equidistant spine articulations freestanding on non-elevated distal portion of LAP; dorsal and ventral lobes merged by sharp, acute kink proximally into continuous volute; gap between spine articulations and distal edge of LAP narrow, slightly increasing in width ventralwards. Ventral edge of LAP with very large, moderately deeply incised, concave tentacle notch.

Inner side of LAP with large, very slender ridge; dorsal part of ridge straight, oblique; ventral part almost vertical, merged with ventral portion of LAP and connected with dorsal part by gently rounded kink; no spurs on inner side of distal edge of LAP; inner side of tentacle notch very large. No perforations or furrow discernible.

Paratype supplements and variation

GZG.INV.78537 is a dissociated distal LAP; approximately twice wider than high; well in agreement with holotype; outer surface with very coarsely meshed stereom; trabeculae merged into shorter and

even less regular vertical stripes than in holotype. Three spine articulations similar to those observed in holotype but with dorsalward increase in size. Ventral edge of LAP with very large, but shallow tentacle notch.

Ridge on inner side of LAP straight, oblique, slender, merged ventrally with ventral portion of LAP.

Remarks

These LAPs are unambiguously assignable to Ophiologimus on account of the very large tentacle notch combined with the spine articulations freestanding on the non-elevated distal portion of the LAP and the simple ridge on the inner side devoid of conspicuously thickened parts. Among the fossil LAP types assigned to this genus, the above is unique in combining a coarsely meshed outer surface stereom with lenticular, oblique spine articulations and a continuous ridge on the inner side with the ventral part merged with the ventral portion of the LAP.

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.