Sericominolia Kuroda & Habe, 1954

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 : 54

Genus Sericominolia Kuroda & Habe, 1954

Ethminolia (Sericominolia) Kuroda & Habe, 1954: 84 [Japanese], 92 [English].

Type species

Minolia stearnsii Pilsbry, 1895 (original designation), Recent, Japan.

Diagnosis

Shell relatively thin, depressed turbiniform to trochoid-turbiniform, of moderate size (diameter up to 14.0 mm); whorls rounded or weakly shouldered, periphery at or below mid-whorl, base flatter; sculpture fine, comprising close-set spiral lirae and microscopic axial pliculae; umbilicus open, its rim thickened, usually (not always) with distinct internal funicle ending in reflected callus on columella lip, often differentially coloured; outer lip simple, interior smooth.

Operculum corneous, relatively thick, multispiral, but not tightly so; whorl overlap narrow, peripheral fringe narrow; spiral microsculpture lacking.

Radula with base-plates of rachidian and lateral teeth relatively robust; inner marginal tooth transitional with reduced cusp; cusps of marginals 3–10 largest, with a large bluntly lanceolate central denticle bearing 1–2 smaller denticles at its outer base.

Ctenidium bipectinate, anterior portion unattached.

Remarks

Sericominolia comprises an assemblage of small to medium-sized umboniine species, typically with relatively thin, somewhat glossy shells, a moderately raised spire, rounded periphery and indented suture, with a fine sculpture of close-set spiral lirae and microscopic axial pliculae on the adapical surface. The base is umbilicate and there may or may not be an umbilical funicle. The colour patten often varies greatly, but is commonly variegated or mottled, and narrow spiral capillary lines with opaque white flecks are frequent. The umbilical funicle is often differentially pigmented. Currently, only two species are referred to the genus, the type species S. stearnsii (Pilsbry, 1895) and S. vernicosa ( Gould, 1861) , both described from Japanese waters, but this number will undoubtedly grow as further species are studied in greater detail. Likely referable to this genus are Minolia eilikrines Melvill, 1891 from the Philippines, Talopena gloriola Iredale, 1929 from New South Wales and Trochus vitiligineus Menke, 1843 from temperate Australia.

Preliminary molecular studies ( Williams et al. 2024) indicate that there is much cryptic diversity within Sericominolia with significant geographical substructure. At this stage, therefore, it is unwise to envisage wide-ranging species and multiple synonyms. Splitting rather than lumping is likely to be needed.

Material referable to Sericominolia is common shallow-water habitats in New Caledonia, but it has proved difficult to interpret. In addition to the already described S. lifuana ( Fischer, 1878) , I have identified two undescribed species which exhibit consistent differences that permit separation from S. lifuana s. s. These occur at somewhat greater depths than is typical for the largely lagoonal S. lifuana , and are instead associated with reef passes and habitats largely outside the lagoonal system. Even so, the remaining Sericominolia material, all here identified as S. lifuana , quite possibly represents a complex of cryptic taxa. There is considerable variation in size, spire height, width of the umbilicus and the strength of its funicle, as well as in shell pigmentation and pattern, and colour of the funicle. I have been unable to confidently delimit morphologically consistent units within this variation and consider that any further subdivision of this complex is best conducted in the light of molecular data. There is some evidence of geographic structure within this morphological variation, particularly between Chesterfield-Bellona material and Grande Terre material, but this too is difficult to evaluate given the geographical distance between the populations and the absence of molecular data.