Petraeomastus neumayri ( Hilber, 1883 )

Chen, Zhong-Guang, Zhou, Yi, Dai, Yu-Ting, Wu, Xiao-Ping & Ouyang, Shan, 2024, A review of three taxonomically confused species of Petraeomastus Möllendorff, 1901 (Gastropoda: Stylommatophora: Enidae) from the Jinshajiang River Valley, with the description of a new species, Journal of Natural History 59 (1 - 4), pp. 11-28 : 13-17

Petraeomastus neumayri ( Hilber, 1883)

( Figures 1 (A), 2(A–C), 3, 4(C))

Buliminus (Napaeus) neumayri Hilber, 1883, p. 1357 , pl. 4, figs. 7, 8

Buliminus (Mirus) neumayri : Möllendorff 1901: 326

Buliminus (Napaeus?) neumayri : Kobelt 1902: 546, pl. 86, figs. 4, 5

Ena (Mirus) neumayri : Yen 1938: 441

Petraeomastus neumayri : Yen 1942: 254

Petraeomastus neumayri : Wu 2018: 178, pl. IV, fig. 19

Material examined

n = 1, BMNH 1912.6.27.26–28 , Batang, west China, identified by T.C. Yen; n = 11, 24_NCU_XPWU_AN01–11, 1 km west of Jinshajiang River Bridge [金沙江大桥以西 1 km], Mangkang County [芒康县], Changdu City [昌都市], Xizang Autonomous Region [西藏自 治区], China, 99.000°E, 29.761°N, collected by Zhong-Guang Chen, Meng-Hua Li and Jin-Sheng Mou, 17 August 2023 .

Diagnosis

Shell sinistral, medium width (<12 mm), uniformly reddish brown; umbilicus narrowly open. Penial caecum present, subglobular. Bursa copulatrix ovoid, with stalk, well defined. Habitat is exposed rock walls.

Redescription

Shell. ( Figure 2 (A–C)) n = 11. Shell cylindrical-conic with apex abruptly pointed; shell most swollen at body whorl, sinistral, large, medium width (width <12 mm), thick, solid, semitranslucent, sub-glossy, not speckled, not spirally grooved; 6.75–8.0 whorls. Whorls rather flattened, not shouldered. Post-nuclear teleoconch smooth, polished. Post-nuclear whorls 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, slightly oblique, without tooth, without angular tubercle, adnate. Peristome connected, with a shallow channel at upper insertion; white, thickened, expanded, slightly reflexed. Parietal callus distinct. Columellar margin reflexed. Umbilicus narrowly open. Shell uniformly reddish brown. Apex region coloured like the rest of the shell.

Genitalia. ( Figure 3 ) n = 5. Vas deferens relatively 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; slightly convoluted. Appendicular retractor and penial retractor; biramous; attaching to penis in middle part and to A-1 + A-2; 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 longer than vagina. Vagina short; not swollen; straight; unpigmented. Bursa copulatrix duct long; proximally straight. Bursa copulatrix ovoid, with stalk; without apical ligament; normal in size; with short neck; well defined. Diverticle normally present; longer than bursa copulatrix; unexpanded. Bursa copulatrix and diverticle distinguishable; forked more distally from their base.

Measurements

n = 11. Shell height 21.3–26.1 mm, width 10.1–11.5 mm; aperture height 9.0– 9.8 mm, width 6.6–7.5 mm.

Distribution and ecology

Petraeomastus neumayri is only known from Mangkang County on the right bank of the Jinshajiang River ( Figure 1 (A)). This known distribution refers to the area where live animals, empty shells, or shell fragments have been observed or collected. However, due to the steep terrain of the mountain, it is challenging to collect all observed living animals or specimens. Consequently, the examined specimens referred to in this study were collected from a relatively gently sloped area. The distribution of this species is limited to the lower part of the valley in an area of a few hundred square metres and does not extend to the alpine meadows in the upper part. It inhabits steep rock cliffs together with the land snail Holcauchen markamensis Chen and Zhang, 2000 ( Figure 4 (A–C)), and living snails are almost never seen on the ground. Juveniles are covered in mud.

Remarks

The number of whorls in this species varies greatly, resulting in a significant change in the height of the shell. Hilber (1883) mentioned that the shell of this species is brown, which distinguishes it from all congeners in the region. The type locality of this species was recorded as Batang County. However, Batang was used more generally for the region in the past. This species lives along the right bank of the Jinshajiang River, which is nowadays in Mangkang County.

Figures

Figure 1. Distribution of four enid gastropod species reviewed or described in this study. Coloured or shadowed regions show the distributional range. (A) Petraeomastus neumayri; (B) Petraeomastus desgodinsi; (C) Petraeomastus markamensis; (D) Petraeomastus gigas sp. n.; (E–F) The location of the research region in China. ① 1 km west of Jinshajiang River Bridge, ② Chaxue Village, ③ southern Batang County, ④ Langdaquka.

Figure 2. Species of Petraeomastus redescribed in this study. (A) P. neumayri in original description (Hilber 1883); (B) P. neumayri, NHMUK 1912.6.27.26–28 (Wu 2018); (C) P. neumayri, 24_NCU_XPWU_AN01; (D) P. desgodinsi, syntype, NMW 1955.158.24105 (Wood and Gallichan 2008; Ablett et al. 2019), copyright Amgueddfa Cymru – Museum Wales; (E) P. desgodinsi, 24_NCU_XPWU_AN012; (F) P. markamensis in original description (Chen and Zhang 2001); (G) P. markamensis, NHMUK 1912.6.27.22–25 (Wu 2018); (H) P. markamensis, 24_NCU_XPWU_AN036.

Figure 3. Genital anatomy of P. neumayri. (A) back view; (B) aperture view. A-1: most proximal section of penial appendix; A-2: penial appendix section between and thicker than A-1 and A-3, usually bulbshaped; A-3: section of the penial appendix connecting proximally A-2 and distally A-4; A-4: thinnest part of the penial appendix between A-5 and A-3; A-5: distal part of the penial appendix, more or less swollen; AR: retractor muscle of the appendicular branch; At: atrium; BC: bursa copulatrix; BCD: bursa copulatrix duct; D: diverticle of the bursa copulatrix duct; Ep: epiphallus; EpC: epiphallic caecum; Fl: flagellum; FO: free oviduct; P: penis; PC: penial caecum; PR: retractor muscle of the penial branch; Va: vagina; VD: vas deferens.

Figure 4. Adjacent environment and habitat of living individuals of Petraeomastus land snails. (A&B) Environment of the Jinshajiang River Valley, left side: Batang County, right side: Mangkang County; (C) living specimens of P. neumayri; (D) living specimens of P. desgodinsi; (E) living specimens of P. markamensis; (F) living specimens of Petraeomastus gigas sp. n. and P. markamensis.