Sinployea australis Climo, Mahlfeld & Roscoe, 2025

Mahlfeld, Karin, Climo, Frank & Roscoe, David, 2025, Systematics, conservation status, and biogeography of 16 new species of Sinployea Solem, 1983 (Gastropoda: Charopidae) from New Zealand, Zoological Journal of the Linnean Society 204 (1) : -

Sinployea australis Climo, Mahlfeld & Roscoe sp. nov.

( Figs 11, 16, 33C, 36, 45)

Korukoura ‘australis’ McGuinness 2001: 604; Hitchmough 2002: 125.

Charopidae sp. 30 (NMNZ M.078966) Hitchmough et al. 2007: 85; Spencer et al. 2009: 216; Mahlfeld et al. 2012: appendix 1.

Material examined: New Zealand, South Island : NMNZ M.078966, holotype ( Figs 33C, 36), Southland, Invercargill ,

Waihopai Reserve , 46°22′59.593″S, 168°21′41.336″E, C. Broomfield, April–May 1983 .

Other material examined: Known only from holotype.

Description: Shell small, thin, and fragile, 2 mm wide and 1.09 mm high at approximately three whorls, moderately finely ribbed, loosely coiled, narrowly umbilicate, and low spired. Shell of translucent whitish colour, spire broadly convex. Protoconch of 1.25 convex whorls, translucent, 534 μm wide; sculpture consisting of five thin, crisp, widely spaced spiral lirae. Teleoconch of 1.75 rapidly expanding, convex whorls, slightly flattened ab- and adaxially. Sculpture consisting of numerous calcareous, thin, primary axials traversed by fine spiral lirae; spirals approximately one-third of the width of primary axials and forming microscopic beads at intersections with even finer secondary axials, about five axials per interspace. Primary axials crested with a very fine periostracal lamella, often worn off (78 axials on first teleoconch whorl). Umbilicus 510 μm wide (D/U 3.92); spirals prominent around umbilical well. Suture deep. Aperture obliquely oval, 891 μm high; columella short and a little curved and reflected, lip simple.

Reproductive anatomy: Unknown.

Etymology: From Latin australis , southern, in reference to the southern distribution of the species.

Distribution: South Island, Southland, Invercargill.

Ecology: Temperate floodplain podocarp forest?

Related species: The combination of finely ribbed shell with a relatively wide umbilicus for the NZ Sinployea species and pale buff shell colour distinguishes S. australis from the other colour-patterned and unicoloured shell species. Two unicoloured species occur in the South Island: S. australis and S. maitai (Richmond Range, SE Nelson). The other unicoloured white, golden, and brown species occur in the North Island: S. capensis (Cape Kidnappers) , S. hikurangi (Mount Hikurangi and Tokomaru Bay, East Cape; Ngamoko Trig at Waikaremoana, and Tairua on the Coromandel Peninsula), and S. accelerata (widespread).

Conservation status: Sinployea australis might have become extinct since it was last collected in the 1980s in Thomsons Bush, Invercargill. Repeated sampling in bush reserves in and around Invercargill has failed to rediscover this species. Collections have been made in Thomsons Bush and other localities nearby by F.J. Brook (2013), K.M. (September 2016 and November 2020), and N. Peterson (November 2020 and February 2021) without re-collecting S. australis . More than 50 samples have been taken from the area in the last decade and have failed to detect this species. We therefore propose that the species be presumed extinct. Figure 2 shows the numbers of Southland collection events that have been made, and none of these detected S. australis . It is possible that major weather events, hydrological habitat changes, and weed spraying in the intervening decades might have destroyed snail colonies.