Helix obnubila Reeve, 1852

Brook, Fred J. & Ablett, Jonathan D., 2019, Type material of land snails (Mollusca: Gastropoda) described from New Zealand by taxonomists in Europe and North America between 1830 and 1934, and the history of research on the New Zealand land snail fauna from 1824 to 1917, Zootaxa 4697 (1), pp. 1-117 : 54

Helix obnubila Reeve, 1852

Pl. 5, fig. D

Reeve, (1851–1854) 1852. Conchologia iconica, 7: species 792, pl. 130, fig. 792.

Type material: Syntype (1), NHMUK 20041001 (dry shell material); ex Museum Cuming (Acc. no. 1829) .

Label details: ‘ N. Zealand, Mus. Cuming’; ‘ H. sigma Pfr’ in Pfeiffers handwriting .

Type locality: ‘New Zealand’ (Reeve 1852 [in 1851–1854]: species 792).

Previous illustrations of type material: Reeve (1852 [in 1851–1854]: pl. 130, fig. 792); Tryon (1885 [from Reeve, 1852]: pl. 26, fig. 27).

Remarks: Reeve’s description of Helix obnubila was based on one or more specimens in the Cuming collection. Helix sigma Pfeiffer , listed as a synonym by Reeve (1852 [in 1851–1854]: species 792) and some later workers, is a nomen nudum. The extant type material of Helix obnubila comprises a single juvenile shell of c. 4.6 whorls, with a relatively thick, dark brown periostracum. It closely matches shells in populations from the vicinity of Christchurch, South Island (e.g., NMNZ M.275675, M.275678), and may have been collected by Frederick Strange during the visit of H.M.S. Acheron in February–April 1849 (see Introduction). Helix obnubila appears to be conspecific with H. igniflua Reeve, 1852 , and has a complex nomenclatural history. Helix obnubila and H. igniflua [= H. lambda ] have been treated as separate species (e.g., Martens 1873; Hector 1873; Hutton 1880; Tryon 1885; Pilsbry 1892 [1892–1893], 1893 [1893–1895]; Powell 1937, 1946 b, 1957, 1962), and obnubila has been listed as a subspecies or variety of igniflua (e.g., Hedley & Suter 1893: 636; Suter, 1902b: 208, 1904a: 64, 1913b: 629). Other workers have recognised a single species only. Hutton (1884b: 203) listed H. igniflua , H. lambda & H. sigma Pfeiffer (= nomen nudum) as junior synonyms of H. obnubila . Suter (1894a: 127) noted “that they are all one and the same species, and that there is not even a possibility of making out a constant variety……The differences in the shell seem to be due to the influence of habitat only. The dentition is the same in both”. Helix obnubila and H. lambda were listed as junior synonyms of H. igniflua by Suter (1894b: 147, 1894d: 256) and Powell (1976: 117, 1979: 317), and this interpretation has been followed in recent systematic lists (i.e., Spencer & Willan 1995; Spencer et al. 2009). However, if H. igniflua and H. obnubila are in fact conspecific, then Hutton’s synonymy takes precedence, under the Principal of the First Reviser (ICZN Article 24.2 Following Pilsbry (1892 [in 1892–1893: 72) this taxon has generally been assigned to Thalassohelix Pilsbry, 1892 , at genus or subgenus level, but preliminary results of a phylogenetic study (M. Kennedy & F. Brook unpub. data) indicate that this placement requires re-evaluation.

Taxonomy: Provisionally treated here as Thalassohelix obnubila (Reeve, 1852) n. comb.

Distribution: New Zealand; eastern and southern South Island, and Stewart Island ( Suter 1913b; Powell 1979 —as Thalassohelix igniflua ).