Scaphander mundus Watson, 1883

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 : 8-15

Scaphander mundus Watson, 1883

( Figs 1–3 ; Table 2)

Scaphander mundus Watson, 1883: 342–343 ; 1886: 643–644, pl. 48, fig. 2; Pilsbry 1893: 251–252, pl. 31, figs 13, 14; Kobelt 1896: 6–7, pl. 2; Smith 1906: 247; Valdés 2008: 674–677, figs 40C, D, 43 (in part).

Scaphander alatus Dall, 1895: 676 , pl. 27, fig. 2; Valdés 2008: 674, 676.

Scaphander vicinus Smith, 1906: 248 ; Annandale and Stewart 1909: pl. 19, figs 5, 6.

Taxonomic history: Scaphander mundus was first introduced by Watson (1883) from shell material collected at 1460 m west of New Guinea island by the Challenger expedition. Watson (1883) described the shells as thin and white, covered with spiral punctuated sculpture and with an outer lip extending in a small posterior projection. Watson (1886) illustrated the species and compared it with S. nobilis , referring to differences in the upper part of the outer lip and general shape of the shell. Dall (1895) described the species S. alatus from a specimen found at 545 m in Hawaii and named it after the wing-like projection of the outer lip of the shell. Dall (1895) again compared this species with S. nobilis , but differentiated S. alatus by having a thicker, less inflated shell. He also referred to S. mundus , but declared the two species impossible to confuse, without adding any further comment. Valdés synonymized the name S. alatus with S. mundus , yet his description and illustrations include specimens of S. mundus ( Valdés 2008: figs 40C, D) and of a distinct lineage ( Valdés 2008: figs 40A, B) here described as a distinct species, namely S. cornus . The latter strongly resembles S. nobilis , with a more inflated posterior half of the shell, and does not match the main features mentioned by Dall (1895) for S. alatus (see below for a detailed description).

Smith (1906) described S. vicinus from shells collected by the Investigator west of Sri Lanka (as Ceylon). He commented on the similarities with S. mundus and S. alatus but considered differences in the sculpture of the shell (punctation) and shape of the posterior outer lip to support S. vicinus as a distinct species. Our observations revealed substantial variation in the spiral sculpture of S. mundus , and in the shape of the posterior part of the outer lip, overlapping with the description of these features in S. vicinus . Therefore, we here consider S. vicinus a junior synonym of S. mundus .

Type material: Scaphander mundus Watson, 1883 — Indonesia: west of Papua, off Aore (= Aru) Islands , Challenger Expedition, station 191, 5°41'00"S, 134°04'00"E, 1463 m, two syntypes, NHMUK 1887.2.9.2181 , H = 24.5, 28 mm, images seen ( Fig. 1A, G ) . Scaphander alatus Dall, 1895 — Hawaii: Albatross Expedition , station 3476, 21°09'00"N, 157°53'00"W, 545 m, holotype, USNM 107161, H = 35 mm, images seen ( Fig. 1B ). Scaphander vicinus Smith, 1906 — Sri Lanka: west of Sri Lanka, Investigator Expedition , station 318, 7°28'00"N, 79°19'30"E, 1984 m, six paratypes, NHMUK 1906.7.21.4–9, H = 26–36 mm, images seen ( Fig. 1C ).

Other material examined: Philippines: east of Luzon, one spc., dissected and sequenced, MNHN-IM-2009-4318, H = 29 mm; one spc., sequenced, MNHN-IM-2009-4319, H = 22 mm. China Sea: southwest of Taiwan, one spc., sequenced, MNHN-IM-2013-50091, H = 18 mm; one spc., sequenced, MNHN-IM-2013-50090, H = 24 mm; one spc., sequenced, MNHN-IM-2013-50039, H = 21 mm; one sh., MNHN-IM-2016-5761, H = 30 mm; one spc., sequenced, MNHN-IM-2013-50089, H = 37 mm; southwest of DongSha, one spc., sequenced, MNHN-IM-2013-61614, H = 29 mm; one spc., sequenced, MNHN-IM-2013-61612, H = 32 mm; South China Sea, off Taiping Island, one spc., dissected and sequenced, MNHN-IM-2013-44305, H = 30 mm; one spc., dissected and sequenced, MNHN-IM-2013-44310, H = 26 mm; one spc., MNHN-IM-2013-44306, H = 22 mm; one spc., MNHN-IM-2013-44308, H = 27 mm; one spc., MNHN-IM-2013-44313, H = 32 mm. Australia: Queensland, Coral Sea Commonwealth Marine Reserve, one spc., dissected and sequenced, AM C.519372, H = 22 mm. New Caledonia: Loyalty Basin, five sh., MNHN-IM-2010-2075, H = 15–22 mm.

Diagnosis: Shell elongated oval, white. Outer lip protruding in a straight wing above the apex. Spiral sculpture composed of separate or interconnected punctuated striations. Rachidian teeth H-shaped. Prostate cylindrical, separated from penial chamber by thin, short prostatic duct. Penial papilla elongate.

Shell ( Fig.1 ): Maximum H observed = 37 mm. Shell oval to oval elongate, widest around centre, only one whorl visible. Aperture as long as shell, narrowing posteriorly. Spire concealed. Posterior edge of outer lip rising in small straight wing above apex. Parietal wall covered with thick, smooth white callus. Spiral sculpture composed of punctuated striations. Punctations oblong, round, elongated, or squarish. Thin, translucent to pale yellow periostracum. Shell white.

Radula ( Fig. 2A–C ): Radular formula 17 × 1.1.1 (H = 29 mm). Lateral teeth curved, with weak denticulation on inner edge. Rachidian teeth H-shaped, central area convex on one side, and slightly concave on the other side; developed pointed-triangular cusps present.

Digestive tract ( Fig. 2D, E ): Salivary glands medium long, surface uneven. Paired gizzard plates kidney-shaped to sub-triangular.

Male reproductive system ( Fig. 2F, G ): Penial chamber cylindrical, bulged towards prostatic duct, lined with soft longitudinal ridges. Muscular penial papilla elongate, covered in warts. Penial chamber separated from prostate by short prostatic duct. Prostate cylindrical, rounded at end.

Ecology: Found between 900 and 1800 m depth. Feeds on foraminifera, tubicolous polychaetes, and small molluscs (present study).

Distribution ( Fig. 3 ): Western Pacific Ocean to Eastern Indian Ocean, from Hawaii ( Dall 1895), New Caledonia ( Valdés 2008), Australia (present study), China Sea, the Philippines ( Valdés 2008), Banda Sea, Indonesia ( Watson 1883), and Sri Lanka ( Smith 1906).

Remarks: Scaphander mundus has often been confused with the new species here described as S. cornus (Indo-West Pacific) (e.g. Valdés 2008) and with S. nobilis (Atlantic, Western Indian Ocean), which explains several misidentifications and reports of S. mundus in the Atlantic (Locard 1897, Marcus and Marcus 1966, Pequegnat 1983). However, as Eilertsen and Malaquias (2013a) first showed, S. mundus and S. nobilis are distinct both genetically and morphologically, and records of S. mundus in the Atlantic should be considered as misidentifications of S. nobilis . Our study revealed a second species first identified as S. mundus by us, which is here described as a new taxon, S. cornus . These two species are not only molecularly divergent (COI uncorrected p -distance of 5.47%–6.46% between S. mundus and S. nobilis and 4.56%–5.74% between S. mundus and S. cornus ), but also show several morphological and conchological differences; the shell of S. mundus is less inflated than in S. cornus and S. nobilis , and the posterior outer lip protrudes above the apex in a shorter and less curved wing-like shape.

The species Bulla insperata Fischer, 1883 (in Locard 1897) was described from shells sampled off the coast of Western Sahara. Locard (1897) commented on its resemblance to Bulla millepunctata Locard, 1987 (a synonym of Scaphander nobilis ; see S. nobilis section) and to S. punctostriatus . Bouchet (1975) synonymized B. insperata with S. mundus in the Atlantic. However, the shell of the type material for B. insperata is more evenly rounded and generally more globose, rather than oval or elongated as in S. mundus . The syntype housed in the Paris Museum (MNHN-IM-2000-27695) resembles some larger and roundish forms of S. punctostriatus , a species that has been referred along the cost of West Africa southwards down to South Africa ( Bouchet 1975, Steyn and Lussi 2005, Herbert et al. 2018). Thus, until further specimens from the Western Sahara matching the morphotype of B. insperata are discovered and studied, we suggest this species to be considered a synonym of S. punctostriatus .

Figures

Figure 1. Shells and SEM image of the shell sculpture of Scaphander mondos. A, Indonesia, west of Papua, off Aore Islands (syntype, NHMUK 1887.2.9.2181, H = 29 mm, images courtesy of the NHMUK). B, Hawaii (holotype, Scaphander alatos, USNM 107161, H = 35 mm, images courtesy of the USNM).C, Sri Lanka (paratype, Scaphander vicinos, NHMUK 1906.7.21.4.9, H = 31 mm, images courtesy of the NHMUK). D, South China Sea, off Taiping Island (MNHN-IM-2013-44305, H = 30 mm). E, Philippines, east of Luzon (MNHN-IM-2009-4319, H = 22 mm). F, Australia, Queensland, Coral Sea Commonwealth Marine Reserve (AM C.519372, H = 22 mm). G, Indonesia, west of Papua, off Aore Islands (syntype, NHMUK 1887.2.9.2181, H = 26 mm, image courtesy of the NHMUK). H, Philippines, east of Luzon (MNHN-IM-2009-4319, H = 22 mm). I, J, Australia, Queensland, Coral Sea Commonwealth Marine Reserve (AM C.519372, H = 22 mm). Scale bar: J = 200 µm.

Figure 2. Anatomical details of Scaphander mondos. A, radula, Australia, Queensland, Coral Sea Commonwealth Marine Reserve (AM C.519372, H = 22 mm). B, rachidian teeth (AM C.519372, H = 22 mm). C, detail of lateral teeth (AM C.519372, H = 22 mm). D, anterior part of digestive tract, South China Sea, off Taiping Island (MNHN-IM-2013-44305, H = 30 mm). E, gizzard plates (AM C.519372, H = 22 mm). F, male reproductive system (AM C.519372, H = 22 mm).G, penial papilla, South China Sea, off Taiping Island (MNHN-IM-2013-44310, H = 26 mm). Scale bars: A, G = 200 µm; B, C = 20 µm; D, F = 1 mm; E = 2 mm.

Figure 3. Geographical distribution of Scaphander cornus, Scaphander mondos, and Scaphander nobilis. Geographical records are based on studied material and reliable literature records.