Ophiolimna lisae, 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 : 69-71

Ophiolimna lisae sp. nov.

urn:lsid:zoobank.org:act:53A4D340-3462-4B83-B996-14E4D2A3F071

Fig. 14 : 1-3

Diagnosis

Species of Ophiolimna with large LAPs displaying a large, conspicuous, straight, oblique, golf clubshaped central ridge with strongly widened, ventro-proximally pointing dorsal tip; second ventral, short ridge almost directly bordering ventral tip of central ridge.

Etymology

Species named in honour of my friend Lisa Walz, who would always find encouraging words to cheer up moments of despair, including those accompanying the terminal phase of this study.

Type material

Holotype GZG.INV.78561.

Paratypes

GZG.INV.78562, GZG.INV.78563 and GZG.INV.78564 from the upper Kimmeridgian Amaral Formation of Trancoso, Portugal

Type locality and horizon

Pointe du Chay near La Rochelle, France; Achilles Subzone, Cymodoce Zone , early Kimmeridgian, Late Jurassic.

Additional material

GZG.INV.78565 (78 dissociated LAPs) from the upper Kimmeridgian Amaral Formation of Trancoso, Portugal.

Description

Holotype

GZG.INV.78561 is a dissociated, large, proximal one; higher than wide; dorsal and distal edges convex; proximal edge concave and slightly angular, devoid of spurs but with narrow band of very finely meshed stereom; ventral seventh of LAP only weakly protruding ventro-proximalwards; outer surface almost entirely covered by coarse, regular vertical striation composed of broad, overlapping lamellae decreasing in size proximalwards and replaced by densely meshed stereom in narrow area bordering the central part of the finely meshed band at the proximal edge of the LAP. Six large, ear-shaped spine articulations in relatively deep notches of the distal edge, overlapped by the strongly undulose distalmost lamella and connected with the latter by the large, conspicuously tongue-shaped ventral lobes of the spine articulations; dorsalward increase in the size of the spine articulations and of the gaps separating them; no gap between spine articulations and distal edge of LAP. Tentacle notch almost indiscernible in external view.

Inner side of LAP with large, conspicuous, sharply defined, prominent, oblique, straight, golf clubshaped central ridge; dorsal tip of ridge strongly widened, pointing ventro-proximalwards; second ventral, well-defined and prominent but short ridge almost directly bordering ventral tip of central ridge but nevertheless sharply separated from the latter; no spurs on inner side of distal edge of LAP; inner side of tentacle notch large, obscured by sediment. Broad, shallow vertical furrow dorsally bordering tentacle notch with series of irregular, medium-sized perforations, with dorsalward increase in gaps separating perforations.

Paratype supplements and variation

GZG.INV.78562 is a dissociated proximal LAP, fragmentary, ventral portion of LAP missing; originally larger and higher than holotype; otherwise well in agreement with holotype.

GZG.INV.78563 is a dissociated median LAP; nearly as high as wide, of rounded aspect; generally well in agreement with holotype. Four large, ear-shaped spine articulations with dorsalward increase in size of gaps separating them.

Inner side of LAP with large, conspicuous central ridge, similar to that of holotype but slightly bent rather than straight; ventral ridge similar to that of holotype; inner side of tentacle notch large, bordered distally by thin, moderately well-defined ridge. Broad, shallow vertical furrow dorsally bordering tentacle notch with series of irregular, medium-sized perforations, distally bordered by poorly defined and dorsally fading ridge.

GZG.INV.78564 is a dissociated distal LAP; slightly wider than high; well in agreement with holotype. Four spine articulations, dorsalmost of which invisible in external view.

Inner side of LAP with large, conspicuous central ridge, similar to that of holotype but slightly bent and merged with ventral ridge; inner side of tentacle notch large and distally bordered by prominent, welldefined ridge. Broad, shallow, poorly defined vertical furrow dorsally bordering tentacle notch with series of irregular, medium-sized perforations, distally bordered by poorly defined and dorsally fading ridge.

Remarks

The highly distinctive outer surface striation and spine articulation morphology leave no doubt as to the assignment of these LAPs to the genus Ophiolimna . On account of its large size and the shape and arrangement of the ridges on its inner side, the LAPs in question are incompatible with any currently known species of Ophiolimna .

Occurrence

Early Kimmeridgian of France and late Kimmeridgian of Portugal.

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.