Alvania undetermined
Creators: name: Amati, Bruno
name: Taviani, Marco
name: Oliverio, Marco
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Littorinimorpha
Rissoidae
Alvania
Alvania undetermined

description: Alvania sp.
(Figs 3; 10C)
Material examined. Only one specimen found in stn COR 2-53 (see Table 1; Figs 3; 10C), unfortunately in a poor state of conservation, in particular the back and the first whorls.
Distribution. Likely Pleistocene, Strait of Sicily, 649 m, (this work).
Description. Shell (Fig. 3) small for the genus, height 2.1 mm, width 1.3 mm, height/width ratio 1.62, ovate-conical with coeloconoid profile. Protoconch paucispiral of 1.5 convex whorls, height 0.312 mm, nucleus diameter 0.112 mm, first half whorl diameter 0.225 mm, maximum diameter 0.275 mm with the illegible sculpture because the protoconch is eroded. Teleoconch of 3.4 convex whorls with incised suture. Axial sculpture on the last whorl of 9 rounded, ortocline ribs, plus the labial varix, as broad as the interspaces and interrupted at the base. Spiral sculpture, on the last whorl of the spire above the mouth, made up of 3 spiral cordlets, surmounting the axial ribs, 1 wavy on the suture line and 4 thinner ones on the base. Large subsutural space devoid of spiral sculpture. Absent umbilical chink. Aperture pyriform, large, height 0.875 mm, height/height aperture ratio 2.40, height last whorl 1.35 mm, height/height last whorl ratio 1.48, peristome continuous, smooth internally, thickened externally by a modest varix. Coloration uniform whitish. Operculum and soft parts unknown.
Remarks. Alvania sp. belongs to a group of shallow water species; the shell collected at stn COR 2-53 (649 m) is quite likely a fossil, probably of Pleistocene age.
Alvania sp. is similar to Alvania maurizioi Chirli, 2006, from the Pliocene of Tuscany, which differs in its larger size, height 3–3.7 mm vs height 2.1 mm in Alvania sp., and the internally slightly lyrate outer lip vs smooth in Alvania sp. (Chirli, 2006: 27, pl. 13, figs 1–10).
Alvania sp. differs from A. pizzinii (Amati et al. 2020: 442, figs 12A–G, 17D–F) in its wider base and a nonceloconoid profile, more robust and fewer ribs (9 vs 12–18 in A. pizzinii), the wavy spiral cordlet on the suture line vs non-wavy in A. pizzinii.
Alvania leopardiana Brunetti & Vecchi, 2012 (Pleistocene of Emilia) is similar to Alvania sp. in its slender shell with an angled profile, a wide subsutural ramp and the same number of spiral cordlets (3 on all whorls). It differs in the convex base vs concave in Alvania sp.; larger size, height 2.3–2.9 mm, width 1.1–1.5 mm vs height 2.1 mm, width 1.5 mm in Alvania sp.; height/width ratio 1.87–2.09 vs 1.62 in Alvania sp.; height/height last whorl ratio1.017 vs 1481 in Alvania sp.; protoconch wider (0.340 mm) and lower (0.269 mm) vs 0.275 mm and 0.312 mm respectively in Alvania sp. (Brunetti & Vecchi 2012: 43, figs 2A–C).
Another very similar species is the fossil Alvania subampulla Zhizhchenko, 1936 (Neogene of Chechnya), originally described as a variety of Alvania montagui (Payraudeau, 1826) [now Alvania discors (T. Brown, 1818)]. Based on original description and figure of A. subampulla (Zhizhchenko, 1936: 189, pl. 19, fig. 18; Fig. 4), its suture is more incised, the whorls more convex, the aperture smaller, the axial ribs on the last whorl are opistocline vs orthocline in Alvania sp., and it seems to have a multispiral protoconch vs paucispiral in Alvania sp. The specimen figured as Alvania sp. B from the Pliocene of Romagna by Tabanelli et al. (2020: 24, 37, pl. 2, fig. 16) is very similar to A. subampulla.
description: Published as part of Amati, Bruno, Taviani, Marco & Oliverio, Marco, 2024, Rissoidae (Mollusca, Gastropoda, Rissooidea) from taphocoenotic assemblages of the Strait of Sicily (Mediterranean Sea) with the description of two new species, pp. 19-37 in Zootaxa 5432 (1) on pages 25-26, DOI: 10.11646/zootaxa.5432.1.2, http://zenodo.org/record/10898484