Pterocyclos jousseaumei (Morgan, 1885)

Tongkerd, Piyoros, Tumpeesuwan, Sakboworn, Inkhavilay, Khamla, Prasankok, Pongpun, Jeratthitikul, Ekgachai, Panha, Somsak & Sutcharit, Chirasak, 2023, Systematic revision of the snorkel snail genus Rhiostoma Benson, 1860 (Gastropoda, Caenogastropoda, Cyclophoridae) with descriptions of new species, ZooKeys 1142, pp. 1-144 : 1

Pterocyclos jousseaumei (Morgan, 1885)

Fig. 56

Rhiostoma jousseaumei Morgan, 1885: 400, pl. 8, fig. 2. Type locality: la haute vallée de Kinta ( Pérak) [Kinta valley, Perak, Malaysia]. Möllendorff 1891: 340. Kobelt 1902: 178. Kobelt 1911: 758, pl. 110, figs 11-13. Laidlaw 1928: 31. Chang 1995: 5 with text figure. Foon et al. 2017: 24, fig. 8f.

Rhiostoma Rhiostoma macalpine-woodsi Laidlaw, 1939: 166, with text figure. Type locality: Sungei Siput, Perak. Sutcharit et al. 2019: 37, fig. 8g.

Type material.

The type specimens Rhiostoma jousseaumei Morgan, 1885 could not be located in the MNHN collection. Lectotype (designation in Sutcharit et al. (2019)) NHMUK 1939.4.13.23 (Fig. 56D ) of Rhiostoma macalpinewoodsi Laidlaw, 1939, from Sungei Siput, Perak.

Other material examined.

Malaysia: Specimen CUMZ 4752 (2 shells; Fig. 56B ) from Ipoh, Perak State . CUMZ 7457 (15 shells; Fig. 56C ) from Tanjung Rambutan, Kinta, Perak State. CUMZ 10213 (5 shells; Fig. 56E, F ) from Gunung Dato, Ipoh, Perak State.

Remarks.

Periostracum thin, corneous, shell varying from uniform colour to dark brown zigzag pattern; periphery with a thin spiral band. Detached-whorl length similar to apertural width. Peristome circular and double or boundary hardly visible; lip thick or thin, and not expanded to slightly expanded. Breathing device with incomplete tube or tubular shape, curved posteriorly and its tip usually attached to preceding whorl. Operculum calcareous, multispiral, and slightly concave on both surfaces.

An operculum accompanied the examined specimen and was also figured in Morgan (1885): it was multispiral and plate-shaped (Fig. 56A, C ). With these observations, we suggest the re-assignment of this species to the Pterocyclos . This species can be separated from Pterocyclos subalatus Sykes, 1903, Pterocyclos spelaeotes (Tomlin, 1931), and Pterocyclos umbraticus (Benthem Jutting, 1949) from peninsular Malaysia in having the apertural lip thickened and usually not expanded (rarely slightly expanded), while the three species (Fig. 57A-C ) tend to have a widely expanded lip (see also Sutcharit et al. 2014). Furthermore, P. subalatus has no detached whorl but has a wide canal-shaped breathing device attached to the preceding whorl; P. umbraticus has a larger shell (width 27 mm), without a detached whorl, and an undulated shell surface.

Laidlaw (1939) stated that R. macalpinewoodsi differed from R. jousseaumei in having a relatively small shell (height 6 mm, width 12 mm), with slightly thickened but not expanded apertural lip, a breathing device channel-like to short tubular [= incomplete tube] shape. Later, Foon et al. (2017) examined several specimens and found an intermediate shell form; the type locality of both nominal species is situated in the Kinta Valley, Perak State, peninsular Malaysia. In addition, the specimens examined herein show a mix between smaller shell (with incomplete tube) and larger shell (with tubular) forms in a single collection locality, with the intermediates as reported in Foon et al. (2017). This distinctive shell size and breathing device could be attributed to intraspecific variation, and examination of more specimens and systematic study will help resolve this issue.

Figures

Figure 56. Shell of Opisthoporus jousseaumei A original figure (after Morgan 1885: pl. 8, fig. 2) B specimen CUMZ 4752 from Ipoh, Perak, Malaysia C specimen CUMZ 7457 from Kinta, Perak, Malaysia D lectotype of " Rhiostoma macalpinewoodsi Laidlaw, 1939 " NHMUK 1939.4.13.23 from Sungei Siput, Perak E, F specimens CUMZ 10213 from Gunung Dato, Ipoh, Perak, Malaysia.

Figure 57. A Pterocyclos subalatus Sykes, 1903, holotype UMZC 1032 from Gunong Inas, Perak, Malay Peninsula B Pterocyclos spelaeotes (Tomlin, 1931), lectotype NMW 1955.158.01107 from Batu Cave, Kula Lumpur, Selangor C Pterocyclos umbraticus (Benthem Jutting, 1949), holotype ZMA 135622 from Maxwell's Hill, Perak, Malaysia D Cyclotus boxalli syntype NHMUK 1894.5.23.1 from Kina Balu E Opisthoporus battambangensis holotype MNHN-IM- 2000 - 35506 from Battambang, Cambodia F Opisthoporus grohi holotype MNHN-IM- 2000 - 35507 from Dak Nong, Vietnam. Photograph: H Wood, NMW (B), M Caballer, A Lardeur and V Heros, MNHN (E, F).