Genus Talopena Iredale, 1918

Talopena Iredale, 1918: 30 .

Type species

Monilea incerta Iredale, 1912 (original designation),?Quaternary to Recent, Kermadec Islands.

Diagnosis

Shell depressed turbiniform to trochoid-turbiniform, stout, size moderate (diameter up to 17.0 mm); whorls rounded, periphery below mid-whorl, base somewhat flatter; sculpture of spiral cords with fine axial pliculae in intervals; umbilicus open, bounded by a thickened spiral band with curved axial pliculae; interior of umbilicus with a low, broad funicle; columella lip thickened basally and at end of funicle; outer lip simple, its 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, long and spathulate, with shallow medial furrow and 1–2 small denticles at outer base.

Ctenidium bipectinate, anterior portion unattached.

Remarks

When proposing Talopena, Iredale (1918) provided no diagnostic characters and merely stated that his new genus represented ‘a well-marked austral series’ that he considered distinct from Monilea Swainson, 1840 . Subsequently, Iredale (1929b) referred a further two species to Talopena, namely Talopena gloriola Iredale, 1929 and Trochus lifuanus Fischer, 1878, but these are species with much finer sculpture than Monilea incerta (Fig. 34D–G) and they lack a broad, peri-umbilical band with curved axial pliculae, and have a narrower funicle within the umbilicus. They are instead referable to Sericominolia . Both Thiele (1929: 57) and Wenz (1938: 319) considered Monilea and Talopena to be distinct at genus-level, whereas Keen (1960: 261) treated Talopena as a subgenus of Monilea . Subsequently, Marshall (1979) considered Talopena to be a synonym of Monilea s. s.

Having examined a large amount of ‘ Monilea s. lat. ’ material from New Caledonia as well as type specimens of several of the taxa currently considered referable to Monilea (MolluscBase 2024), I believe Talopena to be distinct from Monilea and to represent a cluster of nominal species distributed over much of the central Indo-West Pacific, and extending into the eastern Indian Ocean. For comparison, I illustrate the holotypes of the type species of both genera (Fig. 34). In Talopena, the umbilicus is bounded by a single broad, thickened spiral band bearing close-set, curved axial plicae, whereas in Monilea such a band is lacking and the umbilical rim is sculptured by narrower cords similar to those on the base. A further difference is that the interior of the outer lip in Monilea bears strong in-running spiral ridges. In Talopena such ridges are absent and the interior of the outer lip is smooth. Sculpturally, the spiral cords on the spire whorls of Monilea are more distinctly beaded than they are in Talopena . An umbilical funicle is present in both genera, but its strength of development is evidently variable within both genera and within species. The holotype of the type species of Monilea has a particularly well developed umbilical funicle that terminates as a large callus pad extending from the mid-region of the columella (Fig. 34C).

In addition to Talopena incerta, Talopena also includes Trochus belcheri Philippi, 1850 of unknown provenance, Trochus calyculus Wood, 1828 of unknown provenance (figured syntype NHMUK 1878.6.3.1, Fig. 77A–C), Monilea menkei A. Adams, 1855 from Masbate Island, Philippines (holotype, NHMUK 1968180, Fig. 77D–F), Trochus (Monilea) masoni G. Nevill & H. Nevill, 1874, from the Andaman Islands and Monilea philippii A. Adams, 1855, from ‘ China Seas’ (lectotype, NHMUK 1968181, Fig. 77G–I). Whether or not these all represent distinct species is a matter requiring further investigation. Smith (1879) was firmly of the opinion that Trochus calyculus and T. masoni were synonyms. More recently, Patterson et al. (2022) employed the name Monilea masoni for material from the Gulf of Manaar, but the specimen illustrated appears closer to Monilea lentiginosa A. Adams, 1853 .