Petraeomastus desgodinsi ( Ancey, 1884 )

Petraeomastus desgodinsi ( Ancey, 1884) View in CoL

( Figures 1 View Figure 1 , 2 View Figure 2 (D–E), 4(D), 5)

Buliminus desgodinsi Ancey, 1884, p. 387 –388

Buliminus (Petraeomastus) desgodinsi : Möllendorff 1901: 349; Kobelt 1899 –1902: 965

Material examined

n = 1, syntype, NMW 1955.158.24105 , Batang, west China, collected by C.M.F Ancey; GoogleMaps n = 9, 24_NCU_XPWU_AN012–20 , Langdaquka [朗达曲卡], Batang County [巴塘县], Ganzi Tibetan Autonomous Prefecture [甘孜藏族自治州], Sichuan Province [四川省], China, 99.041°E, 29.871°N, collected by Zhong-Guang Chen, Meng-Hua Li and Jin-Sheng Mou, 16 August 2023; GoogleMaps n = 2, 24_NCU_XPWU_AN021–22 , Chaxue Village [茶雪村], Batang County [巴塘县], Ganzi Tibetan Autonomous Prefecture [甘孜藏族自治州], Sichuan Province [四川省], China, 99.075°E, 29.956°N, collected by Zhong-Guang Chen, Meng-Hua Li and Jin-Sheng Mou, 16 August 2023; GoogleMaps n = 13, 24_NCU_XPWU_AN23–35 , southern Batang County [巴塘县城南], Ganzi Tibetan Autonomous Prefecture [甘孜藏族自治州], Sichuan Province [四川省], China, 99.063°E, 29.939°N, collected by Zhong-Guang Chen, Meng-Hua Li and Jin-Sheng Mou, 16 August 2023 GoogleMaps .

Diagnosis

Shell sinistral, width> 12 mm, reddish brown at apex but gradually transitioning to pale greyish on last whorl; umbilicus narrowly open. Penial caecum present, subglobular. Bursa copulatrix tubular, with stalk, poorly defined. Habitat is exposed rock walls.

Redescription

Shell. ( Figure 2 View Figure 2 (D–E)) n = 24. Shell cylindrical-conic with apex abruptly pointed; shell most swollen at body whorl or penultimate whorl, sinistral, large, broad (width> 12 mm), thick, solid, opaque, sub-glossy, not speckled, not spirally grooved; 7.0–8.0 whorls. Whorls rather flattened, not shouldered. Protoconch smooth, polished. Post-nuclear teleoconch smooth. Growth lines distinct. Suture shallow, without narrow band beneath it. Body whorl gradually ascending towards aperture, rounded at periphery. Aperture in a plane, truncate-ovate, oblique, without tooth, with shallow slightly protruding angular tubercle, completely adnate to body whorl. Peristome connected, with a shallow channel at upper insertion; white, thickened, expanded, slightly reflexed. Parietal callus distinct. Columellar margin reflexed. Umbilicus narrowly open. Shell apex region reddish brown, gradually transitioning to greyish white downwards.

Genitalia. ( Figure 5 View Figure 5 ) n = 5. Vas deferens relative short, slightly swollen distally; entering epiphallus apically with distinct demarcation. Epiphallus long; cylindrical; forming numerous loops; externally smooth. Epiphallic caecum present; blunt apically; located near vas deferens entrance. Flagellum short; tubular; proximally normal; with tip pointed. Penis with terminal entrance of epiphallus; clavate; distally tapering. Penial caecum present, subglobular. Penial appendix long; branched off from penis at some distance from atrium; divided into sections including A-1 + A-2, A-3 and A-4 + A-5. A-1 and A-2 fused. A-2 and A-3 not fused. Boundary between A-4 and A-5 indistinct. A-5 long; convoluted. Appendicular retractor and penial retractor long; biramous; attaching to penis middle part and to A-2 of penial appendix; with penial retractor arms arising from diaphragm closed to each other. Additional retractor other than penial or appendicular absent. Muscular band connecting vagina and epiphallus absent. Atrium short; without retractor. Free oviduct almost equal in length to vagina. Vagina long; not swollen; straight; unpigmented. Bursa copulatrix duct long; proximally straight. Bursa copulatrix tubular, with stalk; without apical ligament; normal in size; with short neck; poorly defined. Diverticle normally present; longer than bursa copulatrix; unexpanded. Bursa copulatrix and diverticle distinguishable; forked more distally from their base.

Measurements

n = 24. Shell height 25.3–30.0 mm, width 12.2–13.3 mm; aperture height 10.3–11.5 mm, width 7.7–8.5 mm.

Distribution and ecology

Petraeomastus desgodinsi is distributed in Batang County on the left bank of the Jinshajiang River ( Figure 1 View Figure 1 (B)). It inhabits steep rock cliffs ( Figure 4 View Figure 4 (A,B,D)), and almost never descends to the ground. Juveniles are covered in mud.

Remarks

Wu (2018) provided the photo of specimen numbered NHMUK 1912.6.27.22–25 (reproduced here as Figure 2 View Figure 2 (G)) and identified it as P. desgodinsi . However, upon examination of the type specimen ( Figure 2 View Figure 2 ( D), NMW 1955.158.24105), it was found that P . desgodinsi has a broad and short shell, which is consistent with the new specimens collected from the left bank of the Jinshajiang River . The specimens numbered NHMUK 1912.6.27.22–25 actually correspond to Ena markamensis Chen and Zhang, 2001 ( Figure 2 View Figure 2 ( F)). Petraeomastus desgodinsi can be easily distinguished from E. markamensis by its broader shell, a narrowly opened umbilicus (vs slit-shaped), tubular bursa copulatrix (vs ovoid) and the longer penis. The two species also differ in their habitats, with P. desgodinsi inhabiting only exposed rock walls and E. markamensis inhabiting the mossy ground (see below).