Clostophis laidlawi ( Collinge, 1902 )

Páll-Gergely, Barna & Hunyadi, András, 2022, New and little-known species of Clostophis Benson, 1860 from Southeast Asia (Gastropoda: Eupulmonata: Hypselostomatidae), Raffles Bulletin of Zoology 70, pp. 417-439 : 423

Clostophis laidlawi ( Collinge, 1902)

( Figs. 3–5 )

Hypselostoma laidlawi Collinge, 1902: 83 , pl. 5, figs. 29, 30.

Gyliotrachela laidlawi — Laidlaw, 1933: 214.

Hypselostoma laidlawi — van Benthem Jutting, 1950: 19 (partim).

Paraboysidia laidlawi — van Benthem Jutting, 1961: 36, pl. 8, fig. 2b.

Paraboysidia laidlawi — Maassen, 2001: 74.

Material examined. 92 shells (coll. HA, Figs. 3–5 ), Malaysia, Pahang, 20 km SE of Jerantut, Gua Kota Gelanggi, below Gua Balai , 120 m a.s.l., 3°54.000′N, 102°28.412′E (locality code: 2013/30), coll. A. Hunyadi, 21 January 2013 .

Remarks. This species was originally described to possess four apertural barriers (“a dorsal and ventral one situated on the upper and lower border of the peristome, and two smaller internal teeth, one on the right and one on the left of the peristomial teeth”). Van Benthem Jutting (1950) figured a shell from the British Museum, Natural History (currently NHM) that was collected at the type locality and possessed only two teeth (fig. 9 therein). She also mentioned that the ‘holotype’ of C. laidlawi was in Cambridge and was “so badly broken and delicate that an examination could not be allowed”. However, Collinge (1902) did not mention the number of specimens he examined and did not select a holotype, therefore van Benthem Jutting’s (1950) information about a shell being a holotype is incorrect. We also examined and imaged a shell from the NHM, which was collected at the type locality and originated from the author (Collinge) ( Fig. 6 ). This shell is most probably the same one van Benthem Jutting (1950) also examined, and since it is from the type locality and from the author of the species, we treat it as a syntype of H. laidlawi . In a later paper, based on newly collected material at Ulu Tembeling, van Benthem Jutting (1961) described the species with two apertural barriers as Paraboysidia neglecta . It is evident that there are two distinct species (i.e., H. laidlawi with five teeth and P. neglecta with two) because they were collected syntopically at Ulu Tembeling and no intermediate forms are known.

We collected Clostophis laidlawi at one locality. Among the 92 adult shells, 26 had a ‘normal’ aperture ( Fig. 3 ), whereas the apertures of the remaining 66 shells were slightly or strongly detached from the penultimate whorl ( Figs. 4 , 5 ). This shows that the detached last whorl is a part of the spectrum of variability within a population and suggests that this condition can rapidly develop in Hypselostomatidae .

Although Collinge (1902) mentioned only four apertural barriers, van Benthem Jutting (1961) found five, which matches with our observations. It is probable that Collinge simply overlooked the tiny angular tooth next to the parietal lamella.

Figures

Fig. 3. Clostophis laidlawi (Collinge, 1902), locality 2013/30, specimen 2.

Fig. 4. Clostophis laidlawi (Collinge, 1902), locality 2013/30, specimen 1.

Fig. 5. Clostophis laidlawi (Collinge, 1902), locality 2013/30, specimen 3.

Fig. 6. Clostophis neglectus (van Benthem Jutting, 1961) (syntype of C. laidlawi: NHMUK 20191105).