Paraconocrinus pellati, Roux & Eléaume & Améziane, 2019

Roux, Michel, Eléaume, Marc & Améziane, Nadia, 2019, A revision of the genus Conocrinus d’Orbigny, 1850 (Echinodermata, Crinoidea, Rhizocrinidae) and its place among extant and fossil crinoids with a xenomorphic stalk, Zootaxa 4560 (1), pp. 51-84 : 78-79

Paraconocrinus pellati n. sp.

Fig. 7 G–I, Table 7.

Synonymy. Bourgueticrinus thorenti d’Archiac 1846: 200 –201 (pars)

Conocrinus thorenti Roux, 1978a: 266 , fig. 1Bb; 1978b: 216, fig. 3.

Etymology. Species dedicated to Edmond Pellat (1832–1907), who collected the holotype and five paratypes.

Type locality and type stratum. Biarritz, upper part of Calcaires de Peyreblanque to lower part of Villa Marbella Member, dated as Bartonian (NP 17, rohri zone). The “Rocher du Goulet” of numerous previous authors is now named Gourèpe as a part of Calcaires de Peyreblanque ( Mathelin and Sztrákos 1993) .

Material. Six aboral cups belonging to Pellat’s Collection are housed in the palaeontological collections of the Université Pierre et Marie Curie, Sorbonne Université (SU) in Paris. The best-preserved cup was selected as the holotype (catalogue number: SU.PAL.2018.0.74.1); the others are paratypes B to F(catalogue number: SU.PAL.2018.0.74.2-6). The most complete specimen from the Eocene of Biarritz, figured by Roux (1978a) and housed in the palaeontological collections of the British Museum (catalogue number E 6028) is here considered a paratype (paratype A). Unfortunately, its precise location and stratum are unknown. The main measurements of the seven specimens of the type series are listed in Table 7.

Diagnosis. Aboral cup shape moderately elongated conical with maximum diameter in the upper part of the basal ring; thin sutures between cup ossicles on the external suface, sutures between basals more conspicuous at cup base; proxistele without constriction near cup base. Distal cup face with coarse interradial ribs, ratio of central depression to radial ring diameter ~0.6, muscular synarthries markedly elliptical, IBr1 short with external surface slightly concave and facets convexe.

Descriptions of holotype and paratypes. Aboral cup shape of the holotype moderately elongated conical with maximum diameter in the upper part of the basal ring, slightly decreasing distally in the radial circlet ( Fig. 7G ); thin sutures between cup ossicles on the external suface, sutures between basals more conspicuous at depressed cup base; diameter of cup base relatively large (Db/Dc 0.53) suggesting absence of constriction in proximalmost stalk; ratio basal to cup height 0.8. Distal cup face with coarse interradial ribs, widely opened central depression (ratio of central depression to radial ring diameter 0.66), small axial plug, and muscular synarthries markedly elliptical ( Fig. 7 H–I). Paratype A with proximal stalk, aboral cup and first brachial ring. Four cylindrical columnals preserved, the distalmost with a maximum diameter of 0.16 mm, a height of 1.5 mm and distal facet elliptical (rudimentary synarthry), other columnals with heights of c. 1 mm. Shape of aboral cup as in holotype, sutures inconspicuous or poorly visible on the basal circlet, ratio basal circlet to cup height 0.9, IBr1 of maximum height 0.2 mm with proximal and distal facets convex and external surface slightly concave. Paratype C with abnormal constriction in lower cup, 2.5 mm distal to the cup base. All other paratypes show some variation in cup shape and in distal central depression depth, but always have conspicuous sutures at the aboral cup base.

Remarks. The specimen mentioned by d’Archiac (1846) and collected by Monsieur Thorent at the “Rocher du Goulet” (Biarritz) likely belonged to this species. Small specimens of P. pellati n. sp. (paratypes E and F) resemble P. handiaensis , but larger ones differ in having a more elongated aboral cup, frequently visible sutures between the basals and a distal cup face with widely opened central depression.

Figures

FIGURE 7. Characters of Paraconocrinus n. gen. A–F: Paraconocrinus handiaensis, lower Handia cliff, Biarritz, A–C: holotype, MNHN.F.A69940; D–E: paratype A, MNHN.F.A699641; F: paratype B, MNHN.F.A69942; G–I: Paraconocrinus pellati n. gen., n. sp., holotype, “Rocher du Goulet”, Biarritz, UPMC 5109; J–L: columnals attributed to P. handiaensis, lower Handia cliff, MNHN.F.A49934, J: from distal mesistele, K: from median mesistele, L: from dististele. See Figures 1 and 5 for abbreviations.