Manzonia schmidti, 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 : 26-29

Manzonia schmidti n. sp.

urn:lsid:zoobank.org:act:FA77D785-912C-4EBB-B001-572DE470D973

( Figs. 5A–D ; 6A, B ; 7A–C ; 10D )

Manzonia crassa — Tabanelli et al. 2020: 28, 37, pl. 2, fig. 29 [Pliocene of Emilia-Romagna, Italy] (not Turbo crassus Kanmacher, 1798 )

Type materials and type locality. Holotype ( MNHN.F.A92063), height 2.35 mm, width 1.27 mm, 1 paratype ( MZUB). Type locality: Strait of Sicily, stn COR 2-53, 36.8712° N, 13.1053° E; depth: 649 m.

Material examined. Only two specimens (see Table 1 ; Figs 5A–D ; 6A, B ; 7A–C ).

Etymology. The new species is named after the Schmidt Ocean Institute, a non-profit operating foundation, for its role in promoting the exploration of the deep sea, and the donation in 2021 of the ship Falkor to the Italian National Research Council.

Distribution. Only known from the type material from stn COR 2-53, likely a Plio-Pleistocene sample, and from the Pliocene of central Italy ( Tabanelli et al. 2020, as Manzonia crassa ).

Diagnosis. Manzonia of medium size for the genus (height> 2 mm), with multispiral protoconch, teleoconch with robust axial ribs and thin spiral cordlets; rather protruding small tubercles at the intersections.

Description the holotype. Shell ( Figs 5A–C ; 7A ) of medium size for the genus, height 2.35 mm, width 1.27 mm, height/width ratio 1.85, ovate-conical, slender, robust. Height last whorl 1.57 mm, height/height last whorl ratio 1.50. Protoconch multispiral ( Figs 5D ; 7B ) of 1.8 convex whorls, height 0.287 mm, nucleus diameter 0.075 mm, first half whorl diameter 0.125 mm, maximum diameter 0.300 mm; [first part corroded] a thin suprasutural cordlet on a smooth surface of the last protoconch whorl; flexuose axial growth striae on the last 0.25 protoconch whorl. Protoconch-teleoconch boundary scarcely marked.

Teleoconch of 3.5 convex whorls, slightly angled in the upper third. Suture deeply incised and ondulated, bordered by a first thin spiral cordlet. Axial sculpture on the last whorl of 9 axial ribs, opisthocline, flexuose, rather high, narrower than the interspaces, interrupted on the first basal cord. Spiral sculpture of 11 flat and thin cordlets on last whorl (9 over the aperture), as wide as the interspaces, and five basal cordlets (second and third smaller), each sculptured by 12-13 spiral rows of micropits; interspaces sculptured by 4 spiral threads ( Fig. 7C ). Rather protruding small tubercles at the intersections. Aperture subcircular, adapically narrowed, height 1 mm, height/height aperture ratio 2.35, with duplicate peristome, finely crenulated, internally smooth, crenulated outer lip edge, lip varix more than twice as broad as the ribs, flexuose, opisthocline. Umbilical chink absent.

Colouration monochrome white.

Variability. The paratype ( Figs 6A, B ) is slightly larger: height 2.45 mm, width 1.27 mm, height/width ratio 1.93; 7 spiral cordlets above the aperture and 8 axial ribs. The specimen figured by Tabanelli et al. (2020: 37, pl. 2. fig. 9) from the Pliocene of Romagna, is slightly smaller: height 2.3 mm; width 1.1 mm; height/width ratio 2.09.

Remarks. The paratype has an incomplete protoconch ( Figs 6A, B ). Manzonia schmidti n. sp. belongs to a group of species of shallow waters. The two specimens from stn COR 2-53 (649 m) are quite probably fossils; given the Pliocene age of the specimen figured by Tabanelli et al. (2020: pl. 2, fig. 29) holotype and paratype may be of either Pliocene or Pleistocene age.

M. schmidti n. sp. differs from Manzonia scalaris ( Du Bois, 1831) , from the Miocene of W Ukraine ( Du Bois 1831: 47, pl. 3, figs 40, 41; see also Kowalke & Harzhauser 2004: 123, fig. 8D; TămaȘ et al. 2013: 62, fig. 3b; Garilli & Parrinello 2014: 382, fig. 3A) in its 11–12 spiral cordlets on the body whorl vs 7–8 in M. scalaris ; higher height/width ratio, 1.85–1.93 vs 1.70–1.80 in M. scalaris ; smaller aperture with higher height/height aperture ratio, 2.33–2.47 vs 2.05 in M. scalaris ; last whorl narrower; more convex whorls with no subsutural shoulder.

M. schmidti n. sp. differs from Manzonia crassa (Kanmacher, 1798) (e.g., Moolenbeek & Faber 1987: 4–7, pl. 1, figs 3–5; Kowalke & Harzhauser 2004: 123, fig. 8C; Chirli 2006: pl. 20, figs 5–10; Scaperrotta et al. 2009: 37, 5 unnumbered figures; Garilli & Parrinello 2014: 382, fig. 3F, G; Landau et al. 2018: 275, figs 103 1a–1d) ( Fig. 6C ) in the fewer axials (9) and spirals (11–12) on the body whorl vs 8–20 and 14–20, respectively in M. crassa ; the small rather protruding tubercles at the intersections vs flat, very little protruding in M. crassa ; the convex whorls devoid of subsutural shoulder vs present in M. crassa ; aperture less elongated than in M. crassa . The microsculptures also differs: spiral cordlets each carved with 12–13 spiral rows of pits and with narrower interspaces carved with 4 threadlets vs 7–8 spiral rows of pits and 2–3 threadlets in the interspaces in M. crassa .

Figures

FIGURE 5. Manzonia schmidti n. sp. stn COR 2-53, A–D. Holotype, height 2.35 mm, width 1.27 mm; (A–C) shell; (D) detail of the first whorls (MNHN.F.A92063).

FIGURE 6. Manzonia spp. A, B. Manzonia schmidti n. sp. stn COR 2-53, paratype, height 2.35 (approx. 2.45) mm, width 1.27 mm (MZUB); C. Manzonia crassa (Kanmacher, 1798), Marettimo Is. (Sicily), 30 m depth, height 2.5 mm (BA).

FIGURE 7. Manzonia schmidti n. sp. A–C. Stn COR 2-53, holotype, height 2.35 mm, width 1.27 mm. (A) Shell. (B) Detail of the protoconch microsculpture, same specimen. (C) Detail of the teleoconch microsculpture, same specimen (MNHN. F.A92063).

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).