Euonyma laeocochlis ( Melvill and Ponsonby, 1896 )

Herbert, David G., 2006, Rediscovery of the type species of Euonyma (Subulinidae) and observations on South African species of Gulella (Streptaxidae), with description of two new species (Gastropoda: Eupulmonata), Journal of Natural History 40 (17 - 18), pp. 1063-1081 : 1064-1067

Euonyma laeocochlis ( Melvill and Ponsonby, 1896)

( Figures 1–4 ) Subulina laeocochlis Melvill and Ponsonby 1896, p 316 , Plate 16, Figure 3 . Type locality:

‘‘Humansdorp, St Francis Bay’’, E. Cape Province, South Africa. Euonyma laeocochlis: Pilsbry 1906, p 39 , Plate 10, Figure 68; Connolly 1912, p 214; 1939,

p 337. Euonyma loeocochlis [sic]: Sturany 1898, p 62.

Material examined

Type material. Lectotype, ‘‘ Humansdorp , St Francis Bay’ ’, E. Cape, South Africa ( BMNH 1902.7.30.19).

Additional material. All NMSA. South Africa, E. Cape: Baviaanskloof Wilderness Area, Kougaberg plateau above Geelhoutbos , 800–1000 m, grassland/fynbos, leg. D. Clark , 1999 (V8524); same, 33 u 40.0769S, 24 u 12.6829E, grassy fynbos with numerous rocks and stones, under stones, leg. D. Herbert, 10 October 2000 (V8594); same, 33 u 40.4959S, 24 u 12.5899E, fynbos, under stones, leg. D. Herbert, 10 October 2000 (V8620); same, 33 u 43.1369S, 24 u 17.1239E, grassy fynbos, under stones, leg. D. Herbert, 10 October 2000 (V8572); same, 33 u 41.0569S, 24 u 18.4209E, near trig point, 941 m, grassy fynbos, under stones, leg. D. Herbert, 10 October 2000 (V8624); same, above Grass Neck , 33 u 40.3139S, 24 u 19.8059E, grassy fynbos, under stones, leg. D. Herbert, 10 October 2000 (V8622) ; same, Grass Neck , 33 u 38.8769S, 24 u 20.9209E, thicket/fynbos transition, under stones and amongst leaf-litter, leg. D. Herbert, 9 October 2000 (V8645).

Distribution and habitat

Described from ‘‘ Humansdorp’ ’, but currently known only from the Kougaberg, Baviaanskloof Wilderness area, E. Cape, South Africa ( Figure 4 ); under stones in grassy fynbos at altitudes from 500 to 1000 m .

Remarks

Melvill and Ponsonby’s description of this species was based upon two specimens collected in ‘‘Humansdorp, St Francis Bay’’, E. Cape, one of which, the lectotype (designated Connolly 1939) ( Figure 1 ), is in the Natural History Museum, London ( BMNH 1902.7.30.19). [The location of the other specimen is unknown—it is not present in either the National Museum of Wales or the Manchester Museum (Rowson pers. comm., March 2005), both of which contain other Melvill types.] Although these two specimens were said to have been part of a larger sample, none of this additional material appears to have been deposited in South African museums .

In the more than 100 years since its description, no further specimens of this species have come to light. The absence of additional material, despite an interest in shell collecting at the Albany Museum, Grahamstown, in the first half of the 20th century, suggested that the species was a habitat specialist, which was either now extinct or perhaps confined to habitats of limited extent, the nature of which remained unknown. The type locality, ‘‘Humansdorp, St Francis Bay’’, given by Melvill and Ponsonby (1896) almost certainly related to the general area of origin, rather than a precise locality, and is thus of limited value in locating a species of this kind.

Fortuitously, in 1999 some land snail specimens sent to me for identification by Mr Derek Clark, warden of the Baviaanskloof Wilderness Area, E. Cape, proved to be examples of E. laeocochlis . Pursuing this new evidence, I subsequently visited the Baviaanskloof area in 2000 and found the species to be moderately common there, living under stones in grassy fynbos on the summit regions (500–1000 m) of the Kougaberg, in the area between Geelhoutbos and Rooihoek, on the southern side of the valley ( Figure 4 ). The Baviaanskloof lies within the broader Humansdorp District and it possible that this represents the area in which the original specimens were collected. Grassy fynbos is a plant community characteristic of the eastern region of the fynbos biome, occurring both in coastal lowlands and on mountains ( Cowling and Richardson 1995). The absence of records from the much more accessible lowland localities suggests that E. laeocochlis is restricted to montane grassy fynbos habitats, which are largely remote and difficult to access. These will be somewhat cooler than coastal localities and benefit from more frequent mist and cloud (mean annual precipitation. 800 mm; Schulze 1997). The species was not found at lower altitudes in the Baviaanskloof system where the vegetation changes variously to succulent thicket, Nama Karoo, and savanna, with isolated patches of forest in protected gorges.

The only figure of the species published to date is that of Melvill and Ponsonby (1896) (reproduced by Pilsbry 1906, Plate 10, Figure 68), which is poor and inadequate. I therefore take this opportunity to refigure the BMNH lectotype ( Figure 1 ) and provide also an illustration of a fresh specimen in good condition ( Figure 2 ). Connolly (1939) gave the length of the species as 30.4 mm, but the largest specimen in the newly acquired material measures 35.5 mm in length.

Connolly (1939) drew attention to the significance of E. laeocochlis as the type species of Euonyma Melvill and Ponsonby, 1896 , pointing out that the referral of other large southern African subulinids to this genus may not be justified. Verdcourt (1968) reiterated this more strongly in relation to East African subulinids, stating ‘‘there is no evidence whatever that the larger species are really congeneric with the type of Euonyma …’’. Euonyma laeocochlis has a distinctively acute apex ( Figure 3 ), whereas most other supposed Euonyma species, including all those occurring in southern Africa, have a bluntly rounded apex. In this regard E. laeocochlis resembles members of the genus Subuliniscus Pilsbry, 1919 , with which Connolly (1939) postulated it might be synonymous, and Oreohomorus Pilsbry, 1919 . However, in these taxa the embryonic whorls are reported to have strong spiral sculpture, a feature that is entirely lacking in E. laeocochlis . The embryonic shell in the latter species, after an initially smooth first whorl, bears only axial riblets. Connolly (1939) speculated that the other local subulinids that he placed in Euonyma may need to be referred to a new or alternative genus (genera), but he wisely refrained from pursuing this on account of the lack of anatomical data, not only for E. laeocochlis , but for all local ‘‘ Euonyma ’’ species. The rediscovery of the type species of Euonyma now provides material which can be studied in an attempt to resolve these uncertainties. A number of live-collected specimens were obtained and the soft parts preserved for anatomical examination. Samples were also preserved for molecular study.

Conservation

In the light of this new information, the threat status of the species has been assessed in terms of the current IUCN criteria ( IUCN 2001). An application for red-listing as ‘‘Endangered B1’’ has been submitted. Fortunately, the Baviaanskloof has been identified as a priority area for conservation ( Boshoff et al. 2000).

Figures

Figure 4. Euonyma laeocochlis (Melvill and Ponsonby, 1896) distribution: black triangles represent site records; contours at 500 and 1000 m.

Figures 1–3. Euonyma laeocochlis (Melvill and Ponsonby, 1896). (1) Lectotype, BMNH, length 30.4 mm. (2) Livecollected shell, NMSA V8572, length 32.5 mm. (3) Apex of previous, NMSA V8572.