Cyclotus boxalli (Godwin-Austen, 1893)

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

Cyclotus boxalli (Godwin-Austen, 1893)

Fig. 57D

Rhiostoma boxalli Godwin-Austen, 1893: 32, 33, fig. 1a-c. Type locality: Near Kina Balu; Palawan. Kobelt 1902: 538, 539. Sutcharit et al. 2019: 13, 14, fig. 3b, c.

Pterocyclos boxalli - Vermeulen and Liew 2022: 65, 66, fig. 34a-d.

Type material.

Syntype NHMUK 1894.5.23.1 (1 shell; Fig. 56A ) from near Kina Balu [Mount Kinabalu, Sabah, Malaysia] and syntype NHMUK 1895.12.5.34 (1 shell) from Palawan [Palawan Islands, Province of Palawan, Mimaropa Region, The Philippines].

Remarks.

Originally this species was thought to belong to Rhiostoma , and this classification was followed by Kobelt (1902) until the recent type catalogue ( Sutcharit et al. 2019). The type specimens (Fig. 57D ; see also Sutcharit et al. 2019: 3b, c) appear clearly distinct from the generic diagnosis by having a calcareous operculum with slightly concave outer and inner surfaces, being multispiral, and lamella not elevated. The outer peristome of the breathing device is expanded as a wing at the upper junction and has a short tubular shape, located in the suture and away from the apertural lip; the inner peristome has a shallow incision. In addition, a short, detached whorl and a broadly expanded lip are also present in this species.

Recently, this species was relocated to the Pterocyclos ( Vermeulen and Liew 2022); however, it has a shallow incision on the inner peristome, the outer lip expanded with a wing, it has a short tubular breathing device, and the operculum is plate-shaped, without elevated lamellae or deep grooves on the lateral fringe. These unique characters suggest that this species is more similar to Cyclotus than Petrocyclos (see also Table 2 , Fig. 5 ). Because of all these differences, we suggest the re-assignment of this species to the genus Cyclotus .

Figures

Figure 5. Comparison of breathing device and operculum characteristics among the five genera that closely resemble Rhiostoma. The specimens and opercula represented herein are the type specimen or topotype of the respective type species of each genus; Pterocyclos: P. rupestris Benson, 1832 (lectotype UMZC I. 102070, no locality data), Spiraculum: S. hispidum Pearson, 1833 (specimen NHMUK 1906.4.4.72, from Khasi, Teria Ghat), Rhiostoma: R. haughtoni Benson, 1860 (syntype UMZC I. 103445, from Moulmein), Cyclotus: C. variegatus Pearson, 1833 (specimen NHMUK 1896.6.7.34 - 35, from Palawan), Opisthoporus: Cyclostoma taylorianum Pfeiffer, 1851 = junior synonym of Pterocyclos biciliatum Mousson, 1849 (specimen NHMUK 20210200 for shell, from Basan, Sarawak) and Pterocyclos tener Menke, 1856 (NHMUK ex. Cuming collection for operculum, from Cochin China), and Ptychopoma: Cyclophorus chinensis Moellendorff, 1875 (lectotype SMF 39415, from Lushan bei Kiukiang, China). Red arrows indicate the expansion of outer lip at upper junction of the peristome. Blue arrows indicate breathing tubes (apertural tube in Rhiostoma and sutural tubes in Spiraculum and Opisthoporus).

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).