Tylorhaphe, Herbert, 2024

Herbert, David G., 2024, The Umboniinae (Mollusca: Gastropoda: Trochidae) of New Caledonia, with descriptions of two new genera and eight new species, plus an additional new species from the Bismarck Sea, European Journal of Taxonomy 973, pp. 1-143 : 106

Genus Tylorhaphe gen. nov.

urn:lsid:zoobank.org:act:A38706D5-CFD1-4CE0-AE02-16E86950F65E

Type species

Tylorhaphe luteopicta gen. et sp. nov.

Diagnosis

Shell small (diameter <7.5 mm), depressed trochiform, umbilicate; subsutural cord well developed, beaded or with raised nodules; periphery roundly angled or keeled; peri-umbilical region with radiating pliculae and often with strong spiral cords; umbilical margin angled, delineated by beaded cord; umbilicus lacking funicle; outer lip often descendant in mature specimens and aperture with low subterminal thickening internally and externally, and with shallow subperipheral concavity; protoconch relatively large (diameter 195–230 µm).

Operculum corneous, multispiral with well-developed, radially striate peripheral fringe; spiral microsculpture present.

Radula with well-defined tooth base-plates in central field, that of rachidian quadrate; inner marginal tooth transitional, its cusp reduced, with small denticles; second marginal clearly the largest tooth, with robust cusp bearing large sharply triangular central denticle with additional smaller denticles at its base on both sides.

Etymology

From the Greek words ‘ tylos ’ (τύλΟς), m., a knob or nodule, and ‘ rhaphe ’ (ραφή), f., a seam; in reference to the beaded subsutural sculpture. Gender feminine.

Remarks

This new genus equates to Clade 1 of Williams et al. (2024), which includes sequence data for one of the paratypes of the type species (MNHN-IM-2009-23261). Whereas umboniines generally live in shallow-water habitats (mostly intertidal to a depth of 50 m), species of Tylorhaphe gen. nov. primarily inhabit deeper-water environments, extending to over 300 m. Additional species that may prove to belong to this genus include Solariella illustris Sturany, 1900 from the Red Sea and Solariella nektonica Okutani, 1961 from Japan.

The genus Inkaba Herbert, 1992 from the south-western Indian Ocean is similar in having beaded subsutural sculpture, but its radula differs in that there is no one dominant marginal tooth and the cusps of the inner marginals are ovate rather than trigonal, and have denticles of more uniform size, without a large, sharply triangular central denticle. In addition, the latero-marginal plate is cuspless in Inkaba and the operculum lacks spiral microsculpture. In the genus Antisolarium Finlay, 1926 from New Zealand, the shell is of similar size to Tylorhaphe gen. nov. and it has a beaded cord at the shoulder and around the umbilicus, but the radula differs in that the marginal teeth have a triangular expansion of the tooth shaft beneath the recurved cusp, creating a distinct food groove (pers. obs.). In addition, no one marginal tooth is dominant and the cusps of the inner marginals are elongate-ovate rather than triangular, and they have a bluntly rounded central denticle with a series of smaller, more uniformly sized denticles on the outer margin.