Alvania ismar, Amati & Taviani & Oliverio, 2024

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, Zootaxa 5432 (1), pp. 19-37 : 23-25

Alvania ismar n. sp.

urn:lsid:zoobank.org:act:FC365EB2-2DFE-41A8-9F93-09C0F242B35F

( Figs 2 ; 10A )

Type material and type localities. Holotype ( MNHN.F.A92062), height 2.87 mm, width 1.7 mm ( Fig. 2 ; 10A ), stn COR 2-53, Strait of Sicily, 36.8712° N, 13.1053° E; depth: 649 m.

Material examined. One adult specimen found in a fair state of conservation in stn COR 2-53 (see Table 1 ; Fig. 2 ; 10A ).

Etymology. The name is after ISMAR, the acronym of the Istituto di Scienze Marine of the Italian National Research Council (CNR), to recognize its long-lasting role in the exploration of the Mediterranean Sea, used as a noun in apposition.

Diagnosis. Alvania species with a medium sized, ovate-conical shell, with spiral sculpture on the whole teleoconch, strong axial ribs not reaching the base, inner side of the outer lip without denticles; protoconch paucispiral.

Description of the holotype. Shell ( Fig. 2 ) of medium size for the genus, height 2.87 mm, height of last whorl 1.95 mm, width 1.7 mm, height/width ratio 1.69, robust, ovate-conical. Protoconch paucispiral, of 1.2 convex whorls, maximum diameter 0.325 mm (protoconch corroded, sculpture not known). Teleoconch of 3.8 convex whorls, slightly flattened in the median part, suture incised, slightly canaliculated. First 1.5 whorls smooth. Axial sculpture on the last whorl of 14 rounded, slightly opistocline, flexuous ribs, as broad as the interspaces, interrupted at the base. Spiral sculpture of 17 thin cordlets, the one placed on the suture line wider and 7 thinner on the base: the last two barely visible. Three-four wavy cordlets on the maximum diameter, the others straight. Umbilical chink absent. Aperture pyriform, large, height 1.25 mm, height/height aperture ratio 2.30, peristome continuous, smooth internally, thickened externally by a modest varix with sharp edge. Colour whitish with slightly darker axial interspaces.

Distribution. Known only from the holotype, from the Strait of Sicily, likely Pleistocene.

Remarks. Alvania ismar n. sp. is morphologically similar to a group of species (fossil and extant) almost all typical of habitats shallower than 100 m. The single shell collected at stn COR 2-53 (649 m) is quite probably a fossil, likely of Pleistocene age.

Alvania ismar n. sp. is similar to Alvania lachesis (de Basterot, 1825) ( Chirli & Forli, 2021: 136, 352, pl. 106, figs B1–5) allegedly ranging from the Lower Miocene to the Pleistocene of Central Europe: France, Germany, North Sea Basin, Poland, Hungary, Czech Republic, Bosnia, Italy, British Isles and Turkey ( Lozouet et al., 2001: 31; Landau et al., 2018: 256). Alvania ismar n. sp. differs in its less marked spiral sculpture and the axial ribs interrupted before reaching the base vs axial ribs that continue on the whole base in A. lachesis ; the outer lip internally smooth vs lyrate in A. lachesis ; the paucispiral protoconch vs multispiral in A. lachesis (de Basterot 1825: 27, pl. 1, fig. 4).

Alvania ismar n. sp. differs from Alvania brachia Boettger, 1902 , from the Miocene of Romania in its more convex whorls, more numerous axial ribs that do not reach the base; the outer lip, internally smooth vs lyrate in A. brachia ; paucispiral protoconch vs multispiral in A. brachia . ( Boettger 1902: 139), (see also Zilch 1934: 211, pl. 5, fig. 80; Bałuk1975: 79, pl. 9, fig. 12; Kovács & Stein 2023: 20, 31, pl. 1, figs, 1–5).

Alvania ismar n. sp. differs from Alvania curta ( Dujardin, 1837) , from the Miocene of France, in its paucispiral protoconch vs multispiral in A. curta ; the axial sculpture on the last whorl of 14 rounded, orthocline or slightly opisthocline, flexuous ribs vs 16 slightly prosocline ribs in A. curta ; the outer lip internally smooth vs with 4 weak teeth in A. curta ( Dujardin 1837: 279, pl. 19, fig. 5).

Alvania ismar n. sp. differs from Alvania globosa Landau, Ceulemans & Van Dingenen, 2018: 253 , pl. 80, figs 1a–1c, from the Upper Miocene—Lower Pliocene of France, in its less globose shell, with wider axial ribs and less evident spiral sculpture than A. globosa , and in the outer lip internally smooth vs lyrate in A. globosa .

Alvania ismar n. sp. differs from Alvania cioppii Chirli, 2006 , from the Pliocene of Tuscany, by the orthocline, rounded axial ribs, as wide as the interspaces vs slightly opistocline in the holotype (some figured paratypes have orthocline axials on the last whorl, but still slightly opisthocline on the first whorls), more acute and narrower, with interspaces as wide as twice the ribs in A. cioppii ; first whorls obtuse vs more acute in A. cioppii ; outer lip internally smooth vs with teeth in A. cioppii ; suture incised, slightly canaliculated vs conspicuously undulated and canaliculated due to the presence of a cordlet on the suture line, which is larger and separated by major interspaces in A. cioppii ( Chirli 2006: 18, pl. 8, figs 1–12).

Alvania ismar n. sp. differs from Alvania cf cioppii (sensu Dominici et al. 2020: 77) from the Pliocene of Tuscany ( Italy), by its thin spiral cordlets vs wider and flatter spiral cordlets in A. cf cioppii (sensu Dominici et al. 2020); convex teleoconch whorls with incised but non-canaliculated suture and non-angled base vs less convex whorls with canaliculated suture and angled base in A. cf cioppii ; aperture abapically wider vs narrower in A. cf cioppii (sensu Dominici et al. 2020); outer lip internally smooth vs with marked teeth in A. cf cioppii (sensu Dominici et al. 2020); orthocline or slightly opistocline and flexuous axial ribs vs prosocline and non-flexuous in A. cf cioppii (sensu Dominici et al. 2020).

Alvania ismar n. sp. differs from Alvania thalia De Stefani & Pantanelli in De Stefani, 1888 , from the Pliocene of Tuscany ( Italy) in its less convex whorls and less incised suture; more numerous spiral cordlets on the last whorl (17 vs 10 in A. thalia ); outer lip, internally smooth vs striated in A. thalia ( De Stefani 1888: 230, pl. XI, figs 36–37).

Alvania ismar n. sp. differs from the Recent Alvania claudioi Buzzurro & Landini, 2007 in having 8 wellmarked spiral cordlets on the base instead of 6–7 as in A. claudioi ; furthermore, the spiral sculpture on the adapical part of the whorls is as marked as the basal vs weaker, often absent in A. claudioi ( Buzzurro & Landini 2007: 24, fig. 1a–c)

Figures

FIGURE 2. Alvania ismar n. sp., holotype, stn COR 2-53, height 2.87 mm, width 1.7 mm (MNHN.F.A92062).

FIGURE 10. Rissoidae spp. A. Alvania ismar n. sp.Holotype, stn COR 2-53, height 2.87 mm, width 1.7 mm (MNHN.F.A92062); B. Alvania mamillata Risso, 1826 stn COR 2-53, height 2.8 mm (MZUB); C. Alvania sp. stn COR 2-53, height 2.1 mm, width 1.3 mm (MZUB); D. Manzonia schmidti n. sp. Holotype, stn COR 2-53, height 2.35 mm, width 1.27 mm (MNHN.F.A92063).