Charopa planulata Hutton, 1883

Brook, Fred J., Kennedy, Martyn, King, Tania M., Ridden, Johnathon, Shaw, Matthew D. & Spencer, Hamish G., 2020, Catalogue of New Zealand land, freshwater and estuarine molluscan taxa named by Frederick Wollaston Hutton between 1879 and 1904, Zootaxa 4865 (1), pp. 1-73 : 33-34

Charopa planulata Hutton, 1883

Pl. 4, figs. A, B

Hutton, 1883. New Zealand Journal of Science, 1: 477.

Type material. Lectotype (designated by Climo & Mahlfeld 1998: 2), CMNZ M12773 [ex M1039], and paralectotypes (2), CMNZ M1039 [ex ZS 671] (dry shells).

Label details. CMNZ M1039—‘ Auckland, T.F. Cheeseman Coll.’

CMNZ molluscan catalogue details. M1039—‘ Allodiscus planulatus Hutton, Auckland (old number ZS 671)’.

Type locality. ‘ Auckland (T. F. Cheeseman)’ ( Hutton 1883g: 477, 1884b: 181).

Previous illustrations of type material. Radula teeth illustrated by Hutton (1884b: pl. 9, fig. J) probably from type material; Climo & Mahlfeld (1998: fig. 1A—lectotype).

Remarks. Hutton submitted a description of this species to the Transactions and Proceedings of the New Zealand Institute issue for 1883, but publication was delayed until May 1884 ( Hutton 1884b: 181), and was preempted by a brief description in an account of a meeting of the Philosophical Institute of Canterbury ( Hutton 1883g: 477). There has been considerable confusion over the identity and distribution of Charopa planulata , as indicated by synonymies of Climo & Mahlfeld (1998) and Marshall & Barker (2008: 83, 85, 115, 116). Following misidentifications by Pilsbry (1892 [in 1892–1893]: 67; 1893 [in 1893–1895]: pl. 3, figs. 4–6), planulata was generally assigned to Allodiscus Pilsbry, 1892 at subgenus or genus level, and Hutton’s species name was misapplied to several different taxa, and interpreted as having a wide distribution in New Zealand (e.g., Suter 1913; Powell 1979). Climo & Mahlfeld (1998) stated that all previous records of planulata except the type material were of other species, and they reassigned Charopa planulata Hutton, 1883 to genus Chaureopa Climo, 1985 .

Charopa planulata Hutton, 1883 is possibly conspecific with Chaureopa microumbilicata Climo, 1985 . Type material of the former taxon has a shell of up to 2.7 mm diameter at 4.0 whorls, with a slightly elevated spire, an almost closed umbilicus, teleoconch sculpture of crisp, closely-spaced, sigmoidal radial ribs, and a smooth, glossy protoconch of 1.3–1.4 whorls and maximum diameter of 0.53–0.60 mm. Chaureopa microumbilicata , with a holotype from Kauaeranga Valley, Thames, attains a slightly larger size than the type material of planulata (max. diameter of 3.15 mm at 4.6 whorls), but has similar shell shape and teleoconch sculpture. Shells of microumbilicata generally have a narrowly open umbilicus c. 8–13% of maximum shell diameter (e.g., AIM MA84935, MA96690, NMNZ M.62443, M.62444, M.78793, M.97634, M.186395, M.186508, M.301462), but some populations in Hunua Ranges and Thames, southeast of Auckland, contain shells that have the umbilicus almost closed, as in the type material of planulata (e.g., AIM MA84932, MA97021, NMNZ M.78794). Protoconch size in microumbilcata is also variable, ranging from 0.54–0.74 mm in maximum diameter, and 1.3–1.7 whorls. The two taxa have overlapping distributions: planulata was described from material collected in Auckland; microumbilicata has a sparse distribution in the northeastern North Island between Waiwera, north of Auckland, and Bay of Plenty (AIM and NMNZ collection records).

Current taxonomy. Chaureopa planulata (Hutton, 1883) — Climo & Mahlfeld (1998: 1), Spencer et al. (2009: 215).

Distribution. New Zealand; North Island, recorded from Auckland only by Climo & Mahlfeld (1998), but if synonymous with Chaureopa microumbilicata Climo, 1985 it has a wider, albeit sparse, distribution in the northeastern North Island, between Waiwera and Bay of Plenty.