Paraconocrinus rhodanicus, Roux & Philippe, 2021

Roux, Michel & Philippe, Michel, 2021, Early Miocene stalked crinoids (Echinodermata) from the southern Rhodanian basin (southeastern France). Paleoenvironments and taxonomy, Zootaxa 5052 (3), pp. 301-331 : 325

Paraconocrinus rhodanicus n. sp.

Fig. 12G–K , 13 , Table 8

Type material. 26 Co not figured ( MHNL 20062728) + 4 Co figured ( MHNL 20062727) .

Etymology. Reference to the Rhodanian basin.

Additional material. 1 AC, 1 Co from Vedène.

Diagnosis. As in description.

Type stratum. Late Burdigalian.

Type locality. Place du Palais des Papes in Avignon .

Description. 30 Co (quantitative characters given in Table 8 ) corresponding to a stalk length of 62.5 mm. Co from distal stalk with proximal facet having one or more projections ended by rhizoid insertion at one ( Fig. 12G ) or both sides ( Fig. 12J–K ) of fulcral ridge. Co from mesistele without rhizoid, more elongated (1<H/D<1.5) with oval (D/d <0.85) synarthries (Fig. 14I). Distally, Co with weaker H/D (tending to 0.7), narrower (D/d tending to 2.5) spindle-shaped synarthries ( Figs.12G, J ) with more robust rhizoid socket ( Fig. 12J ). Synarthrial facets of classical Conocrinus type (see Roux et al. 2019) with a deep 8-shaped ligament fossa; fulcral ridge of two segments with axis hollowed, regular crenularium reaching ~20 small Cr on each side and bordered by slightly depressed ligament areas ( Fig. 12H ).

Worn material from Vedène presumedly belonging to P. rhodanicus n. sp. Oblong aboral cup, preserved H 6.9 mm, D maximum 4.0 mm, stalk insertion 1.98 mm. Co with H 2.70 mm, D 2.95 mm and d 2.10 mm.

Remarks. Paraconocrinus rhodanicus n. sp. is a small species with distal Co articulated by narrow synarthries of fulcral ridge bordered by slightly depressed areas as in most species of the genus Paraconocrinus ( Merle and Roux 2018; Roux et al. 2019). The Co figured from the Middle Miocene near Turin (see especially Albus 1931 and Manni 2005) differ in having a larger size and more massive shape. As previously usual, isolated Miocene rhizocrinid Co had been attributed to the most classically cited Eocene species: “ Conocrinus ” thorenti (d’Archiac 1846) or “ Conocrinus ” pyriformis (Münster in Goldfuss, 1826). “ Conocrinus ” seguenzai Meneghini, 1875, known only from aboral cups from the Miocene of Piedmont ( Noelli 1900; Manni 2005), is the only rhizocrinid species clearly identified, but the published figures are too imprecise to attribute it to one of the genera distinguished by Roux et al. (2019). Although very worn, the aboral cup from Vednes, which may belong to P. rhodanicus n. sp., differs markedly from “ Conocrinus ” seguenzai.

Occurrence in southeastern France. Avignon (Place du Palais des Papes), Les Angles?, Vedène?, Late Burdigalian, Early Langhian?

Figures

FIGURE 12. Isocrinid and rhizocrinid columnals. A–K: from Palais des Papes in Avignon; A–C: Metacrinus berthei (MHNL 20.062719), A–B: symplexies with anomalous 4-symmetry, C: distal internodal from a young individual; D–F: Papacrinus avignonensis n. gen., n. sp. (MHNL 20.062726), D: oblique distal view, E–F: oblique proximal view, F: close up of cirrus socket; G–K: Paraconocrinus rhodanicus n. sp. (MHNL 20.062727), G–H: columnal from dististele, G: proximal view, H: close up of fulcral ridge, oblique view, I: columnal from middle mesistele, J: columnal from proximal dististele, proximal view, K: columnal from proximal dististele, side distal view; L: Gastecrinus viticolis n. gen., n. sp. from Vigne Gaste (Istres), aboral cup (MHNL 20.062729). Scale bar equals 1 mm in A–F and L, 0.5 mm in G and I–K, 0.1 mm in H.

FIGURE 13. Variations in columnal general shape of Paraconocrinus rhodanicus n. sp. from the Palais des Papes in Avignon. See Fig. 2G–H for abbreviations. Values in mm, except for ratios.