Alvania pizzinii Amati, Smriglio & Oliverio, 2020

Amati, Bruno, Appolloni, Massimo, Giulio, Andrea Di, Scuderi, Danilo, Smriglio, Carlo & Oliverio, Marco, 2020, Revision of the Recent Alvania scabra (Philippi, 1844) complex (Mollusca, Gastropoda Rissoidae) from the Mediterranean Sea with the description of a new species, Zootaxa 4767 (3), pp. 415-458 : 442-444

Alvania pizzinii Amati, Smriglio & Oliverio n. sp.

( Figs 12 A–G; 13; 17D, F; Table VIII)

Other references.

Alvania scabra ; Bogi et al., 1983: 6, fig. 10.

Alvania sororcula ; Giannuzzi Savelli et al., 2002: 113, figs 470, 471; Scaperrotta et al., 2012: 54, 5 unnumbered figs; Perna, 2013: 65, 2 unnumbered figs; Scaperrotta et al., 2019: 143, pl. IV, fig. M.

Type material. Holotype MNHN IM-2000-33933 , H 2.3 mm, W 1.25 mm ( Figs 12 A–B; 17D–F); 4 paratypes ( BA), type locality: Levanzo Is., Sicily, 31 m depth, Central Tyrrhenian Sea.

Other material examined. Corsica: Century Port, 30–40 m depth, ix.1989, 2 sh ( CS-PM). Sicily: Ustica Is., 35 m depth, 5 sh ( BA); Marettimo Is., 31 sh ( BA); Marettimo Is., Cattedrale Cave, 37°56’45”N 12°4’42”E, 28 m depth, 236 sh ( BA, MO); Skerki Bank, 30 m depth, 2005, 2 sh ( CS-PM); Linosa Is., Secchitella, 20 m depth, 3 sh ( CS-PM); Linosa Is., loc. Faro, 35 m depth, 6 sh ( DS); Lampedusa Is., 20 sh juv. ( BA); Lampedusa Is., 30 m depth, Posidonia intermatte, 1991, 2 sh ( MO); Lampedusa Is., Punta Madonna, 20 m depth, 1 lv, 11.viii.1990 ( RC). Italy: Capraia Is., 110 m depth, 8 sh ( MO); Capraia Is., 75–80 m depth, 1 sh ( BA); Capraia Is., 200–280 m depth, 4 sh ( BA); off Fiumicino, 110 m depth, 2 sh ( CS-PM); off Fiumicino, 100 m depth (in Roman amphora), 3 sh ( MO).

Distribution. Known from the Central-Western Mediterranean ( Scaperrotta et al. 2012 as Alvania sororcula ) ( Fig. 13 ), where empty shells only have been collected at 20–280 m depth. The shells from deeper bottoms (Capraia Is., Italy, 110–280 m depth and off Fiumicino, Italy, 100–110 m depth) have quite probably been drifted from shallower bottoms. Found sympatric with A. scabra , A. lucinae , A. scuderii and A. sororcula .

Diagnosis. Small shell with stepped outline, slightly turriculate. Whorls with wide subsutural ramp. Spiral microsculpture absent. Spiral cord V absent.

Description (data on the holotype in parentheses). Shell ( Figs 12 A–G; 17D–F) small for the genus, height 1.87–2.40 mm (2.30) mm, width 1.10–1.37 (1.25) mm, H/W ratio 1.65–1.84 (1.84), ovate-conical. Protoconch ( Fig. 17E ) paucispiral, with moderately twisted nucleus, of 1.3-1.5 (1.4) convex whorls, height 0.27–0.32 (0.32) mm, nucleus diameter 0.10–0.12 (0.11) mm, first half whorl diameter Do 0.20–0.24 (0.22) mm, maximum diameter DM 0.30–0.37 (0.35) mm. Sculpture of a dozen spiral rows of close-set, rounded microtubercles ( Fig. 17E ). Teleoconch of 3–4.1 (3.6) convex, angled whorls, suture impressed. Axial sculpture on the last whorl of 12–18 (18) slightly prosocline ribs plus the labial varix, narrower than the interspaces and sharply interrupted at the base. Spiral sculpture same strength as axial, of equidistant cords, 7–8 (8) on the last whorl, with 3 (3), exceptionally 4, above the aperture and 4–5 (5) on the base. Cords II and IV starting after protoconch/ teleoconch boundary; cord I absent; cord III appearing at 1.4–2 (1.45) whorls (Table VIII); wide subsutural ramp. Small rounded tubercles at the intersections; interspaces quadrangular. Microsculpture of only growth lines ( Fig. 17F ). Narrow umbilical chink. Subsutural ramp devoid of sculpture. Aperture pyriform, large, height 0.80–0.92 (0.90) mm, H/Ha ratio 2.34–2.70 (2.55), peristome continuous, smooth internally, thickened externally by a modest varix with sharp edge. Colouration translucent yellowish with large subsutural brownish quadrangular blotches. Operculum and soft parts unknown.

Etymology. This species is named after Mauro Pizzini, our dear friend recently passed away who greatly contributed to micromollusc taxonomy.

Remarks. The examined materials showed negligible morphological variation. Maximum height in the examined material 2.40 mm; Giannuzzi-Savelli et al. (2002: 113, figs 470, 471) reported (as A. sororcula ) two conspecific shells from Bocche di Bonifacio, the largest stated as 3.4 mm high (which we suspect might be an error). In the specimens with the lowest H/W ratio the sculpture is usually more robust. The columellar wall sometimes covers the last spiral cord (VII). All examined specimens of A. pizzinii n. sp. (320 shells, including 212 adults) lacked cord I, with the exception of four specimens (4 adults out of 144 adult shells in the same sample) from Marettimo Is., with cord I appearing at 2.2–2.5 whorls. Some shells are monochrome yellowish-orange or brownish.

A. pizzinii n. sp. differs from A. scabra by its stepped outline, the lack of spiral cord I (always present in A. scabra ); the lack of spiral microsculpture on the teleoconch (always markedly present in A. scabra ), the spiral cord V never present vs rarely present above the aperture in A. scabra .

A. pizzinii n. sp. differs from A. sculptilis in having the cords II and IV starting after the protoconch/ teleoconch boundary; cord I not starting; cord III appearing at 1.4–2 whorls vs cords II, IV and V starting after the protoconch/ teleoconch boundary; cord III appearing at 2.2 whorls; cord I appearing after 1.2–2.5 whorl in A. sculptilis (or cords II and IV starting after protoconch/ teleoconch boundary; cord III appearing after 0.25–2 whorls; cord I starting after 1.2–2.5 whorl; cord V not starting).

A. pizzinii n. sp. differs from A. lucinae in the protoconch sculpture of a dozen parallel rows of closely set, broadly rounded but not homogeneous microtubercles, vs ca. 10 parallel rows of broadly rounded but not homogeneous microtubercles, with spiral threadlets in the interspaces; teleoconch spiral cord I always absent vs always present in adults of A. lucinae ; tubercles at the intersections small and rounded vs large and spinose, particularly on cord III in A. lucinae ; spiral microsculpture absent on teleoconch vs present in A. lucinae .

A. pizzinii n. sp. differs from A. sororcula by being more robust; the fewer axials on the last whorl (12–18 vs 25–29 in A. sororcula ); teleoconch cord III appearing at 1.4–2 whorls vs 0.7–1 whorls in A. sororcula ; cord I always absent vs always present in A. sororcula ; spiral microsculpture absent on teleoconch vs present, weak on spiral cords in A. sororcula .

A. pizzinii n. sp. differs from A. josefoi by its more slender outline; the teleoconch spiral cord I always absent vs always present in A. josefoi ; fewer axials on the last whorl (12–18 vs 19–32 in A. josefoi ); spiral microsculpture absent on teleoconch vs very fine spiral threadlets between the spiral cords in A. josefoi .

A. pizzinii n. sp. differs from A. scuderii by its larger size (1.87–2.4 mm, mean 2.16 mm vs 1.55–2.1 mm, mean 1.81 mm in A. scuderii ; colouration (translucent yellowish with large subsutural brownish quadrangular blotches, or monochrome orange-yellowish or brownish vs brownish background with dark brown spiral cords in A. scuderii ); cord I always absent vs always present in A. scuderii .

Three species of the Alvania scabra -complex are currently accepted from the eastern Atlantic, and are briefly discussed below for comparison: Alvania canariensis ( d’Orbigny, 1840) , Alvania angioyi van Aartsen, 1982 , and Alvania grancanariensis Segers, 1999 . Future studies may reveal more undescribed species, as happened with some other genera of rissoids (e.g. Alvania , Manzonia: Amati, 1987, 1992 ; Moolenbeek & Faber, 1987; Rolán, 1987a, 1987b; Gofas, 1990, 2007, 2010; Rolán, & Fernandes, 1990; Bouchet & Warén, 1993; Hoenselaar & Goud, 1998; Cordeiro & Ávila, 2015). This is suggested by the single shell of Alvania sp. discussed below.

Figures

FIGURE 12. Alvania pizzinii n. sp. A, B. Holotype MNHN IM-2000-33933, Levanzo Is. (Italy), height 2.3 mm. C, D. Capraia Is. (Italy) 200–280 m depth, height 2.25 mm (BA). E. Lampedusa Is. (Sicily), height 2.35 mm (MO). F. Capraia Is. (Italy) 200–280 m depth, height 2 mm (BA). G. Lampedusa Is. (Sicily) 30 m depth, height 2.3 mm (MO).

FIGURE 13. Distribution based on the material examined and checked literature data. Red dots, Alvania scuderii Villari, 2017. Light-blue dots, Alvania pizzinii n. sp.

FIGURE 17. Alvania spp. (SEM). A–C. Alvania scuderii Villari, 2017, Linosa Is. 35 m depth (Italy), height 1.69 mm (CS-PM). A. Shell. B. Detail of the protoconch microsculpture, same specimen. C. Detail of the teleoconch microsculpture, same specimen. D–F. Alvania pizzinii n. sp. holotype, MNHN IM-2000-33933, height 2.3 mm, Levanzo Is. (Italy). D. Shell. E. Detail of the protoconch microsculpture, same specimen. F. Detail of the teleoconch microsculpture and of the subsutural ramp, same specimen. G–I. Alvania grancanariensis Segers, 1999, Maspalomas, Gran Canaria, Canary Islands (Spain) height 1.85 mm (JT, JDO). G. Shell. H. Detail of the protoconch microsculpture, same specimen. I. Detail of the teleoconch microsculpture, same specimen.