Callina waldeni Groh & De Mattia

Mattia, Willy De, Neiber, Marco T. & Groh, Klaus, 2018, Revision of the genus-group Hystricella R. T. Lowe, 1855 from Porto Santo (Madeira Archipelago), with descriptions of new recent and fossil taxa (Gastropoda, Helicoidea, Geomitridae), ZooKeys 732, pp. 1-125 : 71-72

† Callina waldeni Groh & De Mattia sp. n. Figs 215-216, 217

List of synonyms.

1983 Discula (Callina) rotula - Waldén: 267, note p. 273 [partim].

Type material.

MMF 46276, holotype, from loc. typ.; CWDM/1 PT, Porto Santo, E of Vila Baleira, S slope of the hill above Vale do Touro, 50 m W of the oil tanks, excavated Quaternary mixed gravel, 33°03'47"N / 16°19'26"W, 24 m, leg. W. De Mattia & J. Macor, May 24 2015.

Locus typicus.

Porto Santo, Quaternary slope deposits in Vale do Touro, Quaternary mixed gravel, 33°03'51"N / 16°19'20"W, 30 m.

Diagnosis.

Callina species with closed umbilicus and well-rounded rather than angulated or keeled last whorl; granulation arranged along the growth lines and not evenly scattered across the entire shell surface.

Description of the holotype.

The shell is dextral, very solid, hairless, and discoidal to conical in shape. The protoconch is dark brown, with 1.3 to 1.6 whorls and almost smooth except for very fine radial striae. The teleoconch has from 6.4 to 6.7 rapidly increasing whorls. It is whitish in colour, probably bleached. The whorls are slightly convex. The last whorl is rather rounded, neither distinctly angled nor keeled. The external upper surface has very fine but clearly visible, irregularly spaced, growth lines. Small scattered tubercles are present on the upper surface of the teleoconch. These tubercles are arranged along the growth lines. Small and rather densely set (exclusively along the growth lines) tubercles are also present on the underside of the last whorl. The last whorl is only slightly wider than the penultimate whorl and only slightly descending towards the aperture. The umbilicus is closed. The aperture is more or less elliptical and the peristome is white and very solid. A strong callous is present along the lower palatal side just behind the aperture. The peristome is interrupted along the palatal area and partially reflected along its basal portion. The palatal area does not show any callouses or thickenings.

Measurements.

D 15.7 ± 0.1 mm (range 15.6-15.8 mm); H 9.1 ± 0.3 mm (range 8.9-9.2 mm); FW 5.6 ± 0.2 mm (range 5.5-5.7); PA 52.4 ± 2.4° (range 51.2-54.4°); NW 7.9 ± 0.3 (range 7.7-8.1) (n = 2). Ratio D/H 1.7; ratio FW/H 0.6.

Distribution.

Callina waldeni sp. n. is only known from the locus typicus. See map in Fig. 217.

Taxonomic remarks.

Waldén (1983: 273) reported in note 72: "A single giant, subfossil specimen (diam. maj. = 15.8 mm, H = 8.9 mm, whorls: 7.9) has been found in Vale do Touro, Porto Santo (Voucher specimen in Funchal Museum)". Waldén clearly introduced the fossil specimen of the MMF collection (n° 46276) as belonging to Callina rotula as also reported in the original museum label depicted in Fig. 215. Callina waldeni sp. n. differs from C. rotula by its larger dimensions and a more conical shape, with slightly more convex whorls. The body whorl is not distinctly angled but rather well rounded. The tubercles are only arranged along the growth lines and not scattered on the entire surface of the shell. The aperture is also less elliptical.

Callina waldeni sp. n. is currently the only known fossil representative of the genus.

Status and conservation.

Extinct before the islands’ scientific exploration in the 19th century, possibly already before human settlement.