Cyathidium chiampoensis, Martinez-Soares & Roux & Giusberti & Gatto & Eléaume & Améziane, 2024

Martinez-Soares, Pablo, Roux, Michel, Giusberti, Luca, Gatto, Roberto, Eléaume, Marc & Améziane, Nadia, 2024, New Eocene species of the crinoid genera Holopus and Cyathidium (Cyrtocrinida: Holopodidae) from north-eastern Italy, Zootaxa 5541 (4), pp. 401-437 : 413-414

Cyathidium chiampoensis sp. nov.

Figures 8A–C ; Table 4

Synonymy. Cyathidium sp. Frisone et al., 2020: 306.

Type material. Two aboral cups including the holotype ( MGP-PD 33229 , Fig. 8A–B ), one well-preserved paratype ( MGP-PD 33230 , Fig. 8C ) .

Etymology. From Chiampo valley, Vicenza province, north-eastern Italy.

Diagnosis. Small species (D<3 mm), aboral cup shape more or less depressed (H/D 0.42 to 1.03), conspicuous growth lines interrupting numerous perpendicular ridges, subcircular adoral face with coarse, short interradial processes. Brachials unknown.

Type stratum. Lower Lutetian tuffite horizon .

Type locality. Cengio dell’Orbo quarry (Cava Boschetto) in the Chiampo Valley, north-eastern Italy .

Description of type series. Aboral cups belonging to small specimens with cup diameter up to 2.72 mm, H equal or substantially lower than D (H/D 0.42), usually D greater than Db. Quantitative characters of the type series listed in Table 4. The holotype, which is the largest specimen, has a curved aboral cup and an external surface showing 8–9 conspicuous parallel growth lines interrupting numerous perpendicular ridges; base smaller than D straight on one side ( Fig. 8A ) and displaying a coarse groove on the other side probably corresponding to the attachment on an irregular substrate ( Fig. 8B ); subcircular adoral face without asymmetry despite the marked cup curvature, external border wide and rounded having coarse outer interradial processes; wide central calycinal cavity. Main characters similar in paratype 1, except cup base more regular than in holotype.

Remarks. The ornamentation consisting of regular growth bands and perpendicular ridges is unknown in congeners. Cyathidium depressum and C. aff. depressum both differ in usually having granulation and more irregular growth bands ( Sieverts 1931; Žítt 1996; Žítt et al. 2014). Cyathidium holopus differs in having variable growth banding either with relatively wide bands ( Rasmussen, 1961: pl. 35, fig. 6) or only numerous very serrated lines ( Donovan & Jakobsen, 2004: fig. 2 f, h), granulation ( Donovan & Jakobsen, 2004: fig. 2 d) or an almost smooth external surface in the specimen from Seymour Island ( Baumiller & Gaździcki 1996). The two latter species and C. vlieksi ( Jagt, 1986: fig. 1) do not show ridges perpendicular to growth lines.

Occurrence. Chiampo Valley (north-eastern Italy), lower Lutetian.

Figures

FIGURE 8. Holopodid aboral cups from Chiampo.A–C: Cyathidium chiampoensis sp. nov., A–B: holotype (MGP-PD 33229), A: oblique lateral view, B: opposite side, C: paratype 1 oblique lateral view (MGP-PD 33230), D–E: Cyathidium sp., D: lateral view MGP-PD 31469, E: lateral view MGP-PD 31471; F–G: holotype of Cyathidium gastaldii (MNHN-F-R68284), F: lateral adoral view, G: close-up of one arm articulation; H–J: aboral cups of Holopus fabianii sp. nov., H–I: holotype (MGP-PD 33232), H: oblique lateral view, I: opposite side; J: lateral aboral view of juvenile paratype 1 (MGP-PD 33233); p: interradial process, r: radial ridge. Scale bars: 1 mm.