Petraeomastus limenghuai Chen, Dai, Wu & Ouyang, 2024

Chen, Zhong-Guang, Dai, Yu-Ting, Wu, Xiao-Ping, Jiang, Jiao & Ouyang, Shan, 2024, A new species of Petraeomastus Möllendorff, 1901, with an atypical shell morphology from the Lancangjiang River Valley in southwest China (Gastropoda, Stylommatophora, Enidae), Zoosystematics and Evolution 100 (4), pp. 1201-1209 : 1201-1209

Petraeomastus limenghuai Chen, Dai, Wu & Ouyang sp. nov.

Figs 2 A , 3

Type.

Holotype. 24_NCU_XPWU_AN 351 , Rumei Town [如美镇], Mangkang County [芒康县], Changdu City [昌都市], Xizang Autonomous Region [西藏自治区], China, 29 ° 36 ' 20 " N, 98 ° 20 ' 40 " E, 2838 m a. s. l., leg. Zhong-Guang Chen, Meng-Hua Li & Jin-Sheng Mou, August 2023.

Paratypes: n = 12, 24_NCU_XPWU_AN 352 –65; n = 2, ZMNH -LB-240003 –04, other information same as holotype .

Diagnosis.

Shell turreted (vs. cylindrical to conical in all congeners), teleoconch ribbed (vs. smooth in all congeners). Flagellum long. Diverticle unexpanded.

Description.

Shell turreted, apex gradually pointed; most swollen at body whorl, dextral, medium-sized, thick, solid, opaque, sub-glossy, not speckled, not spirally grooved; 8.0–8.5 whorls. Whorls rather flattened, not shouldered. Protoconch smooth, polished. Post-nuclear teleoconch ribbed. Growth lines indistinct. Suture rather deep, with an indistinct narrow band beneath it. Body whorl gradually ascending towards aperture, rounded at periphery. Aperture flat, truncate-ovate, oblique, without tooth, with shallow slightly out angular tubercle, completely adnate to body whorl. Peristome connected, with a shallow channel at upper insertion; white, thickened, expanded, not reflexed. Parietal callus distinct. Columellar margin reflexed. Umbilicus narrowly open. Shell multicoloured, post-nuclear teleoconch with light brown backgroud and white ribs; apex region light brown.

Genitalia. Vas deferens relative short, slightly swollen distally; entering epiphallus apically with distinct demarcation. Epiphallus long; cylindrical; rather straight; externally smooth. Epiphallic caecum present; blunt apically; located near vas deferens entrance. Flagellum long; tubular; proximally normal; with tip pointed. Penis with terminal entrance of epiphallus; clavate; uniformly thickness. Penial caecum absent. 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 longer than vagina. Vagina short; not swollen; straight; unpigmented. Bursa copulatrix duct short; 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.

Holotype: shell height 20.6 mm, width 6.7 mm; aperture height 6.4 mm, width 4.7 mm. Paratypes: shell height 19.8–21.2 mm, width 6.0–7.0 mm; aperture height 6.0– 6.6 mm, width 4.2–4.9 mm.

Etymology.

The species is named after Meng-Hua Li, who first discovered the new species and assisted in field surveys.

Vernacular name.

黎氏鸟唇螺.

Distribution and ecology.

Known from the type locality only (Figs 4 , 5 ). Living on branches of bushes alongside P. heudeanus (Fig. 5 ). Although the two species are sympatric, it has been observed that Petraeomastus limenghuai sp. nov. is more common on the shady slopes, while P. heudeanus is more common on the sunny slopes. The distribution of Petraeomastus limenghuai sp. nov. is limited to the middle part of the valley within a few hundred meters and does not extend to the alpine meadows in the upper part. Only two empty shells were discovered at the lower part of the valley, which may have fallen from their original position. In contrast, P. heudeanus is widely distributed in the middle and lower parts of the valley, with numerous individuals observed in close proximity to the river channel.

Figures

Figure 2. Petraeomastus limenghuai sp. nov. and three congeners with typical shell morphology. A. Holotype of Petraeomastus limenghuai sp. nov.; B. P. heudeanus; C. P. neumayri; D. P. xerampelinus.

Figure 3. Genitalia of Petraeomastus limenghuai sp. nov. from both sides. Arrows show the forks.

Figure 4. Six dry-hot river valleys and the sample localities in them. Star. Rumei; green point. Danba; orange point. Maoxian; yellow point. Jiuzhaigou; purple point. Wudu; red point. Wenxian; gray point. Diebu.

Figure 5. Habitat of Petraeomastus limenghuai sp. nov. A, B. The Lancangjiang River Valley at Rumei; C, D. Petraeomastus limenghuai sp. nov. in life.