Rhinovasum, Vermeij, 2024

Vermeij, Geerat J., 2024, Shell-based genus-level reclassification of the Family Vasidae (Mollusca: Neogastropoda), Zootaxa 5405 (4), pp. 526-544 : 533-534

Genus Rhinovasum gen. nov.

Type species. Voluta rhinoceros Gmelin, 1791 , Recent , East Africa ( Figs 4A, B ).

Diagnosis. Shell typically large and solid, maximum length 123 mm; protoconch large, bulbous; last whorl laterally slightly concave in profile; axial sculpture consisting of very short rounded ribs bearing one or two rows of nodules or tubercles on upper part of last whorl, and two spiral rows of shorter nodes near base; spiral cords on central sector broad, with or without very faint nodes or granules; outer lip glazed at edge and on abapertural side, forming lobe or broadly glazed channel at posterior end of aperture; inner side of aperture with very short lirae; columella with three to five thin folds; inner lip often expanded as ventral callus; siphonal canal with dorsally oriented tip.

Included species. Rhinovasum aquitanicum ( Peyrot, 1928) , Early Miocene, France (see Lozouet 2021); R. crosseanum ( Souverbie, 1875) , Madagascar; R. rhinoceros ( Gmelin, 1791) , Kenya and Tanzania; R. rhinoceros attolinoi (Cossignani, 1917) , Zanzibar; R. subpugillare ( d’Orbigny, 1852) , Early Oligocene, France; R. triangulare ( Smith, 1902) , off Durban, South Africa; R. truncatum (G.B. Sowerby III, 1892) ( Figs 4C, D ), off Southeastern Africa; V. tuberculatum ( Gabb, 1873) , Early to Late Miocene, western Atlantic.

Etymology. Greek rhino, nose; and Vasum .

Material examined. Rhinovasum crosseanum : BMNH, Madagascar. R. rhinoceros : BMNH, Zanzibar (sinistral); CAS, Zanzibar (the two latter specimens could belong to the subspecies R.r.attolinoi ); Vermeij collection:Kikambala, Kenya; Nyali, Kenya. R. truncatum : USNM 1190533 and 7092303, off Natal; Vermeij collection, Transkei. R. tuberculatum : UCMP 14670, Cantaure Formation, Venezuela.

Remarks. The new genus Rhinovasum is characterized by a laterally slightly concave last whorl, a narrowly open umbilicus, an extensively glazed outer and inner lip with the latter forming a ventral callus, a broad glazed channel at the posterior end of the aperture, and an elongate, upturned siphonal canal. In the Recent fauna, the group is confined to the western Indian Ocean, but as interpreted here it also includes fossil species from France and the western Atlantic. In the development of a ventral glazed part of the inner lip, Rhinovasum somewhat resembles species of Florivasum , but the ventral shield is more extensive in most species of Rhinovasum than in Florivasum .

I include two species from the warm-temperate coasts of southeastern Africa that diverge from more typically members of Rhinovasum . These species, R. triangulare and R. truncatum ( Figs 4C, D ), have reduced external sculpture, a narrowly glazed outer lip, and no ventral callus; but in other characters they align with the tropical members of the genus from the Indian Ocean. In the future it may be prudent to separate these temperate species as a distinct genus-level taxon.

Martin (1921) described Vasum ceramicum var. from Nyalindung and Cilanang , West Java, Indonesia. These Middle Miocene specimens have short spines, an umbilicus, and three columellar folds. Tomoki Kase (email 21 September, 2018) noted that this taxon does not belong to V. ceramicum , and suggested instead that it might be close to the French R. aquitanicum . This undescribed species might therefore belong to Rhinovasum . If so, it would represent the easternmost occurrence of the genus.

Figures

FIGURE 4. Rhinovasum rhinoceros (Gmelin, 1791) in dorsal (A) and apertural (B) views. Kikambala, Kenya, Vermeij Collection. Rhinovasum truncatum in dorsal (C) and apertural (D) views. Northern Transkei, Vermeij Collection.