Scaphander semicallus, Siegwald & Malaquias, 2025

Siegwald, Justine & Malaquias, Manuel António E., 2025, Bringing light into deep-sea biodiversity: a systematic revision and molecular phylogeny of the genus Scaphander Montfort, 1810 (Gastropoda: Cephalaspidea), with a focus on the Indo-Pacific, Zoological Journal of the Linnean Society 203, pp. 1-60 : 49-51

Scaphander semicallus sp. nov.

( Figs 21 , 34 , 35 ; Table 2)

Scaphander sp.2 — Siegwald et al. 2022.

ZooBank LSID: urn:lsid:zoobank.org:act:3E290146-3337-43B2-9B7A-D367D0DAEE9C

Etymology: Latin, semi; half, callum; callus. Named after the callus covering only the anterior half of the parietal wall of the shell.

Type material: Mozambique: offshore of Inhambane, 23°35 ʹ 12.6″S, 36°05 ʹ 52.8″E, 1092–1195 m, holotype, dissected and sequenced, MNHN-IM-2013-52464 , H = 16 mm .

Diagnosis: Shell, elongate, grey-white. Spiral sculpture composed of small, separate ovoid punctations. Apex rounded, with posterior edge of outer lip rising above it in a small wing. Rachidian teeth X-shaped. Prostate cylindrical, separated from penial chamber by prostatic duct. Muscular penial papilla absent.

Shell ( Fig. 34 ): Maximum H observed = 16 mm. Shell elongate, only one whorl visible. Aperture as long as shell, narrowing posteriorly. Spire concealed. Posterior edge of outer lip rising in small wing beyond apex. Parietal wall covered with thick, smooth white callus in anterior half. Spiral sculpture composed of punctuated striations. Punctations ovoid, separate. Thin, translucent to beige periostracum. Shell grey-white.

Radula ( Fig. 35A–C ): Radular formula 13 × 1.1.1 (H = 16 mm). Lateral teeth curved, with weak denticulation on inner edge. Rachidian teeth X-shaped, with developed cusps, squarish ends.

Digestive tract ( Fig. 35D, E ): Salivary glands short and small; surface uneven. Paired gizzard plates kidney-shaped.

Male reproductive system ( Fig. 35F, G ): Penial chamber cylindrical, lined internally with longitudinal ridges between genital opening and prostatic duct. Eversible penial papilla located at prostatic duct entrance; penial papilla thin, with apical tip rounded, covered in soft warts and wrinkles. Penial chamber separated from prostate by thin prostatic duct, widening towards prostate. Prostate oval, rounded at end.

Ecology: Found between 1092 and 1195 m depth. Feeds on foraminifera (present study).

Distribution ( Fig. 21 ): Mozambique in the Western Indian Ocean.

Remarks: This species is known from a single specimen collected in Mozambique at bathyal depths. Its elongate shell is similar to the non-angular form of the Atlantic Scaphander gracilis Watson, 1883 (Locard 1897, Siegwald and Malaquias 2022), but can be distinguished easily by its parietal callus, which covers only the anterior half of the parietal wall, instead of the entire wall as in S. gracilis . Based on estimates of COI uncorrected p -distances, the two species are 9.27% distinct. The X-shape of the rachidian teeth of S. semicallus is, so far, unique among the genus.

Figures

Figure 21. Geographical distribution of Scaphander semicallus, Scaphander solomonensis, and Scaphander teramachii. Geographical records are based on studied material and reliable literature records.

Figure 34. Shell and SEM image of the shell sculpture of Scaphander semicallus, Mozambique, off Inhambane (holotype, MNHN-IM-2013-52464, H = 16 mm).Scale bar: 100 µm.

Figure 35. Anatomical details of Scaphander semicallus, Mozambique, offshore Inhambane (holotype, MNHN-IM-2013-52464, H = 16 mm). A, radula. B, rachidian teeth. C, detail of lateral teeth. D, anterior part of digestive tract. E, gizzard plates.F, male reproductive system.G, lining of penial chamber. Scale bars:A, G = 100 µm; B = 20 µm; C = 10 µm; D, F = 1 mm; E = 2 mm.