Cataegis taurocrassa

Cataegis taurocrassa (Sacco, 1895)

Fig. 2A–J

Phasianema costatum (Br.) var. taurocrassum Sacco, 1895: 18, pl. 1 fig. 37.

Phasianema (Phasianema) taurocrassum – Moroni 1966: pl. 4 figs 2–3.

ITALY – Emilia-Romagna • 2 specs; Ca’ Piantè; MSF 2352 (H = 4.8 mm), MSF 2353 (H = 7 mm). – Tuscany • 2 specs; Le Colline; MSF 1230 (H = 6.8 mm), MSF 2351 (W = 3.5 mm).

Middle to Upper Miocene, northern Italy.

This species was originally reported from the Calcari a Lucina deposits by Moroni (1966) as Phasianema taurocrassum, and was subsequently cited as such from other Calcari a Lucina sites in the Romagna Apennines (Sami & Taviani 2019; Kiel et al. 2023). Sacco (1895) introduced Phasianema costatum var. taurocrassum for rare specimens from the ‘Helvetian’ of Cinzano in the Turin hills (coll. Rovasenda). Ferrero Mortara et al. (1981) indicated that fossils from Cinzano locality are late Miocene in age. Moroni (1966) wrote that compared to the variants of the Aquitaine and Loire basins, and of the Italian Pliocene, Phasianema taurocrassum (elevated to species level by her) differs in size, by having a thicker shell, different proportion between the spiral cords and the interspaces, growth striae on the cords and interspaces, a the clearer umbilicus that is well delimited by the last spiral cord, a columellar callus with a straight margin that is oblique to the axis and parallel to the direction of the umbilical rim, a much narrower subsutural depression due to the twisted coil and therefore a less slender general shape. We follow her interpretation and consider the respective specimens from the Calcari a Lucina deposits as conspecific with Phasianema taurocrassum.

The genus Phasianema Wood, 1842, however, is a pyramidellid (van Aartsen et al. 1998), based on the Pliocene fossil Phasianema sulcata Wood, 1842, as indicated by van Regteren Altena (1956). We find it questionable that a thick-shelled species like Phasianema taurocrassum should belong to the pyramidellids, although its protoconch, which could provide more definitive evidence, remains unknown. The holotype of Phasianema sulcata illustrated by Wood (1842: pl. 5 fig. 15) is much higher spired than P. taurocrassum, has more numerous spirals with the typical “opisthobranch” pitted grooves, and the outer lip does not show the flaring, reinforced endings of the spiral ribs. Recently, Kaim (2022) re-assigned the Calcari a Lucina specimens of Phasianema taurocrassa to the late Pliocene pyramidellid Carinorbis clathrata. However, that species has high, angular spiral cords crossed by widely spaced axial (oblique) lamellae (see Tabanelli et al. 2022: figs 1–2) very unlike beaded spirals and fine, dense oblique striations of the Calcari a Lucina specimens.

We place Phasianema taurocrassum in the seguenzoid genus Cataegis (as Cataegis taurocrassa) based on its overall shell shape; distinctive, nodular spiral ornament; and the oblique, circular aperture with callused inner lip. The genus Kanoia Warén & Rouse, 2016 was introduced for Cataegis -like species from Caribbean and tropical eastern Pacific deep-water methane-seeps, mainly based on radula characters (Warén & Rouse 2016). As pointed out earlier in the context of a species of Cataegis from the Pliocene of the Philippines, Cataegis appears to have a higher, more conical spire whereas the spire of Kanoia appears somewhat dome-shaped (Kiel et al. 2020), unlike Cataegis taurocrassa.

The most distinctive features of C. taurocrassa, which clearly set it apart from other species of Cataegis, include the ‘twisted’ coiling of the last whorl, the large umbilical slit, and the strongly nodular spiral ornament. Among the extant species, Cataegis tallorbioides Vilvens, 2016, from 543–593 m depth around the Solomon Islands (Vilvens 2016), has perhaps the most distinct nodular ornament, though not as nodular as in C. taurocrassa. In most other extant species of Cataegis, the spiral ornament is granular rather than nodular (McLean & Quinn 1987; Fu & Sun 2006; Vilvens 2016). The Oligocene/Miocene species from the Caribbean region assigned to Cataegis, including Cataegis godineauensis (Van Winkle, 1919), have rather strong spiral ridges that are only finely crenulated (Gill et al. 2005; Kiel & Hansen 2015), in contrast to the strong nodular ornament of C. taurocrassa. The Pliocene Cataegis ramosi Kiel, Aguilar & Kase, 2020 from Philippines differs by lacking an umbilical slit and having non-tuberculate spiral sculpture (Kiel et al. 2020).