A revision of the genus Conocrinus d’Orbigny, 1850 (Echinodermata, Crinoidea, Rhizocrinidae) and its place among extant and fossil crinoids with a xenomorphic stalk Author Roux, Michel Author Eléaume, Marc Author Améziane, Nadia text Zootaxa 2019 2019-02-22 4560 1 51 84 journal article 27431 10.11646/zootaxa.4560.1.3 66d86ea3-e671-4144-b8be-7704010c10e9 1175-5326 2627372 1057AA8B-9221-4045-99A5-8F0CC0F7395B 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 . TABLE 5. Main quantitative characters of external cup morphology in the type series of Conocrinus cahuzaci n. sp. Hc: cup height, Hb: basal ring height, Hpr: maximum height of interradial processes, Ws: maximum width of arm socket, Wr: distal radial width at level of arm socket, Dr: radial ring diameter at level of arm sockets, Drb: diameter at basal/ radial transition, Db: basal ring diameter at cup base. Values in mm.

Characters	Hc	Hb	Hpr	Wr	Ws	Dr	Drb	Db
Holotype	11.55	8.60	1.45	2.35	0.68	3.90	2.50	1.40
Paratype A	10.70	7.90	1.10	1.95	0.56	3.60	2.70	1.50
Paratype B	11.75	9.20	2.30	2.10	0.84	4.90	3.60	1.80
Paratype C	11.80	9.30	1.20	2.50	0.77	4.30	3.40	2.20

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. TABLE 6. Main morphological ratios in aboral cups of the type series of Conocrinus cahuzaci n. sp. See Table 5 for abbreviations.

Ratios	Hb/Hc	Dr/Hc	Drb/Hb	Drb/Dr	Db/Drb	Ws/Wr	Db/Dr
Holotype	0.74	0.34	0.29	0.64	0.56	0.29	0.36
Paratype A	0.74	0.34	0.34	0.75	0.56	0.27	0.42
Paratype B	0.78	0.42	0.39	0.73	0.50	0.40	0.37
Paratype C	0.79	0.36	0.37	0.79	0.65	0.31	0.36

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 .