Pterocyclos diluvium Sutcharit & Panha, 2014

Sutcharit, Chirasak, Tongkerd, Piyoros & Panha, Somsak, 2014, The land snail genus Pterocyclos Benson, 1832 (Caenogastropoda: Cyclophoridae) from Thailand and Peninsular Malaysia, with descriptions of two new species, Raffles Bulletin of Zoology 62, pp. 330-338 : 336

Pterocyclos diluvium Sutcharit & Panha , new species

( Figs. 1 , 3L – P ; Table 1)

Rhiostoma asiphon — Benthem Jutting, 1960: 11. [not Möllendorff, 1893].

Pterocyclos sp. — Kongim et al., 2013: 16: fig. 2A.

Type specimens. Holotype CUMZ 4595 (height 13.9 × diameter 25.4 mm; Fig. 3L ). Type locality: Tam Sumano , Patthalung, Thailand (7°35'183" N, 99°52'80" E) . Paratypes CUMZ 4588 (11 specimens in ethanol, Fig. 3M ) , NHMUK (2 shells), NMW (2 shells), SMF (2 shells) are from the type locality.

Other material examined. Gua Cenderawasih, Perlis, Malaysia CUMZ 3881 (44 shells), 4592 (7 shells, Fig. 3N ). Sungi Jenis, Perlis, Malaysia: CUMZ 3878 (27 shells). Gua Kelam, Perlis, Malaysia: CUMZ 3877 (39 shells), 4587 (6 shells). Wang Kelian, Perlis, Malaysia: CUMZ 3875 (4 shells). Perlis State Park, Malaysia: CUMZ 4586 (10 shells). Khao Loop-chang, Padang Besar, Songkhla: CUMZ 3876 (4 shells). Tam Tone-din, Kuan-Don, Satun: CUMZ 4590 (19 shells; Fig. 3O, P ), 4591 (16 shells), 4866 (4 shells). Tarutao National Park, Satun: CUMZ 4589 (14 shells), 4593 (3 shells), 4749 (6 shells), 4750 (43 shells). Tam Kantiphol, Tung Wa, Satun: CUMZ 4596 (6 shells). Tam Phaya Hong, Kong Ra, Patthalung: CUMZ 4870 (13 shells). Tam Puttha Kodome, Srinagarindra, Patthalung: CUMZ 3812 (9 shells).

Etymology. The specific epithet is from the Latin word “ diluvium ” meaning “inundation or flood”. This is a commemorative name referring to the most devastating flooding in the history of the Kingdom of Thailand in the year 2011.

Diagnosis. This new species differs from P. blandi by having a larger shell, a triangular shaped accessory respiratory device, an upper apertural-lip that is only slightly expanded, and a white to brown shell colour. It differs from the other newly described species, viz. P. frednaggsi Sutcharit & Panha , new species, by having a white to brown shell, a thin periostracum, a triangular shaped accessory respiratory device, and a narrow peripheral band. The differences from Rhiostoma asiphon Möllendorff, 1893 , are the white to brownish shell colour, the low, cup-shaped operculum, and the triangular accessory respiratory structure.

Description. Shell medium to large, depressed, thickened, and widely umbilicated. Apex acute; spire nearly flat; suture wide; whorl 4 – 5 convex becoming increasingly regular. Shell surface with thin growth lines; periostracum thin, corneous to brownish colour. Last whorl rounded and stout, narrow dark brown peripheral band usually present. Shell colour monochrome white, brown or brown zigzag pattern.Aperture rounded with white lip; upper peripheral-lip is slightly expanded near suture. Apertural tube structure triangular shaped, connected with a radial ridge parallel to apertural lip margin. Operculum calcareous, slightly concave inside and multilamellae outside.

Distribution. Pterocyclos diluvium Sutcharit & Panha , new species, has only been located in limestone areas. It is mainly distributed in southern Thailand in Trang, Patthalung, Satun, Krabi, and Songkhla Provinces. In Malaysia, it was recorded from limestone hills in Perlis and Kedah.

Remarks. This new species is superficially similar to R. asiphon with which it could easily be misidentified. Under the name “ Rhiostoma asiphon ”, not in the sense of Möllendorff (1893, 1894), several specimens were reported from many localities from Peninsular Malaysia ( Benthem Jutting, 1960). We examined those specimens and revisited all mentioned localities, and confirmed none of them could be identified as R. asiphon s.s. Moreover, the type specimens of R. asiphon (lectotype SMF 130509 and paralectotypes SMF 130510, 130511, 130512) are clearly distinct from this new species. Especially, with the purplish to black shell colour, the calcareous cup-shaped operculum, and notch shaped apertural tube structure.

Intraspecific variation was observed in the specimens from Tam Tone-din, Satun (CUMZ 4590). This population tended to show a wide range of shell colour variation from dark brown ( Fig. 3P ) to white ( Fig. 3O ). However, the unique accessory respiratory structure and the operculum suggest that the observed colour variation is likely to reflect intraspecific patterns, although this requires further corroboration, such as from molecular data, for confirmation.

Figures

Fig. 1. Distribution map of Pterocyclos species examined in this study. The numbered locality names are detailed in Table 1. The approximate type locality of Pterocyclos subalatus, and Pterocyclos umbraticus, are indicated by locality numbers 3 and 5, respectively.

Fig. 3. A–D, Shell and operculum of Pterocyclos rupestris: A, lectotype UMZC 2359.1; B, paralectotype UMZC 2359.2; C, syntype of var. 3 UMZC 2359.3; D, operculum from same lot of the paralectotype (showing top, side and bottom views). E, F, Specimens of P. blandi from Langkawi Island, Perlis, Malaysia CUMZ 4582. G, Holotype UMZC 1032 of P. subalatus. H–J, Pterocyclos spaleotes: H, lectotype NMW 1955.158.01107, I, paralectotype NMW 1981.118.02705; J, topotype specimen CUMZ 4585. K, Holotype ZMA Moll. 135622 of P. umbraticus. L–P, Pterocyclos diluvium Sutcharit & Panha, new species: L, holotype CUMZ 4595, M, paratype CUMZ 4588, N, specimen from Gua Cenderawasih, Perlis, Malaysia CUMZ 4592; and O, P, specimens from Tam Tone-din, Kuan-Don, Satun, Thailand CUMZ 4590 showing a: O, uniform whitish shell; and P, dark brown colour patterns. Q–S, Pterocyclos frednaggsi Sutcharit & Panha, new species: Q, holotype CUMZ 4594; R, paratype CUMZ 4581; S, specimen from Gua Pulai, Gua Musang, Kelantan, Malaysia CUMZ 4597.