Conocrinus cahuzaci, 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 : 76-77

Conocrinus cahuzaci n. sp.

Fig. 5 I–K, Tables 5–6.

Synonymy. Tormocrinus (g) Roux et al. 2006: 267, table 1.

Etymology. Species dedicated to Bruno Cahuzac (University of Bordeaux), who collected a crinoid fauna (including the type series) that is more diversified than previously expected during his investigations of Eocene sediments in southwest France.

Type locality and type stratum. Miretrain quarry; dark grey marls C6a of Roux et al. (2006), Bartonian (base NP17) at Angoumé near Dax, southwest France .

Material. Four aboral cups, including the holotype (MNHN.F.A69935) and three paratypes (MNHN.F.A69936). Quantitative parameters are listed in Tables 5 and 6.

Diagnosis. Species with an abrupt enlargement of cup diameter at the level of basal/radial transition, five conspicuous and stout hypermorphic interradial processes, coarse and well-developed interradial ribs, ratio of central depression to radial ring diameter 0.44; arm articulatiom of muscular synarthry oval to semi-circular in inner position, ratio of arm socket to distal radial width 0.29.

Description of holotype and paratypes. Aboral cup of the holotype has an abrupt enlargement of diameter at the level of the presumed basal/radial transition, five conspicuous and stout hypermorphic interradial processes of equal size ( Fig. 5I ), coarse and well-developed interradial ribs and a hemispherical central depression ( Fig. 5J ); ratio of central depression to radial ring diameter 0.44; arm articulatiom of muscular synarthry, oval to semicircular in inner position regarding outer edge of the radial circlet ( Fig. 5K ), ratio of arm socket to distal radial width 0.29. Two paratypes (A and C) with five shorter interradial processes of equal size, and the third (B) with one interradial process substantially longer than others.

Remarks. Cups of Conocrinus cahuzaci n. sp., one of the paratypes of C. duperrieri , C. thorenti and C. veronensis share a rounded to semi-circular arm socket in inner position. Conocrinus archiaci differs in having a trapezoidal socket adjacent to the outer edge of the radial circlet. Interradial processes are substantially less developed in C. duperrieri and C. thorenti .

Figures

FIGURE 5. Aboral cups of Conocrinus thorenti (A-D) and other Eocene species from southern France closely related to it. A- D: Conocrinus thorenti, lectotype MNHN.F.R54426, A–B: oblique lateral view, C–D: adoral view, D: closeup of arm socket indicated by arrow in C; E–G: Conocrinus archiaci, Villa Marbella, Biarritz, E–F: specimen MNHN.F.A69934a, E: lateral view, F: oblique adoral view with closeup of arm socket, G: specimen MNHN.F.A69934b, oblique adoral view; H: Conocrinus aff. archiaci, Les Scaffarels near Annot, MHN Nice, Campredon Collection, specimen no. 6, flat arm socket (synostosis); I–K: Conocrinus cahuzaci n. sp., holotype, MNHN.F.A69935, I oblique side adoral view, J–K: adoral views; L–O: Conocrinus duperrieri, marnes à Pentacrines, Côte des Basques, Biarritz, L–N: holotype MNHN.F.R06934 (arrow head indicating segment of radial suture), O: side view of paratype MNHN.F.R06935; bip: broken interradial process, ip: interradial process, ir: interradial rib. See Figure 1 for other abbreviations.