A new species of Pupinidius Möllendorff, 1901 (Gastropoda, Stylommatophora, Enidae) from Jiuzhaigou, Sichuan, China

Abstract Background The genus Pupinidius Möllendorff, 1901 is endemic in China and Nepal and consists of 15 species. China is the distribution centre of it with 12 species being recorded. New information A new species, Pupinidiuspulchellus Chen, Dai, Wu & Ouyang sp. nov. is described from Jiuzhaigou, Sichuan, China. It can be distinguished from congeneric species by the shell with wide and distinct radial stripes; the thin, slightly reflexed and reddish-brown peristome; the unpointed apex; the unfused A-1 and A-2; the sub-globular and well defined bursa copulatrix; the unexpanded diverticle and the presence of epiphallic caecum.

The section of the Bailongjiang River (known as Baishuijiang River in Sichuan) Valley between Jiuzhaigou County and Longnan City is renowned for its exceptionally diverse enid land snails.Since the late 19 and early 20 centuries, several explorers, missionaries and naturalists have collected and described numerous species of family Enidae in the area (Gredler 1898, Sturany 1899, Möllendorff 1901, Yen 1939, Wu and Zheng 2009, Wu 2018).The Jiuzhaigou County is located at the most upstream part of Baishuijiang River and has many unique enid species.However, only one species of the genus Pupinidius, including two subspecies, has been recorded here (Wu andZheng 2009 , Wu 2018).The species diversity of Pupinidius in the region is much lower than in other sections of the Bailongjiang River Valley, which may suggest the presence of other species that have yet to be discovered.In this study, we described a new species of Pupinidius from Jiuzhaigou County, based on shell morphology and genitalia anatomy.The discovery fills the gap between the distribution areas of Pupinidius and enhances our understanding of its diversity.
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Materials and methods
Specimens were collected from Sichuan of China in 2021-2023.Living specimens were initially frozen at -20℃ for 12 hours and subsequently thawed at room temperature for 12 hours to facilitate the extraction of soft parts.The soft parts were then fixed in 70% ethanol.Empty shells were cleaned, dried and preserved at 4℃. Measurements were taken with digital callipers to the nearest 0.1 mm.Whorls were counted as described by Kerney and Cameron (1979).Terminology follows Wu (2018) who defined the genital atrium as proximal.Photographs were taken by camera (A6500, Sony, Minato City, Japan).

Etymology
The specific name is made from the Latin pulchellus for pretty, alluding to the pretty stripes on the shell of this species.Vernacular name: 丽纹蛹巢螺 (Pinyin: li wen yong chao luo).4).Pupinidius nanpingensis is distributed at the west of its habitat, while P. melinostoma is found at the east.The distributions of three species do not overlap and are separated by the Baishuijiang River and its tributary.The boundary between the distribution ranges of the new species and P. nanpingensis is a small unnamed tributary with a deep valley that joins the Baishuijiang River at Shuanghe Town, with the new species downstream, while the P. nanpingensis is upstream.The boundary between the distribution ranges of the new species and P. melinostoma is the Baishuijiang River, with the new species on the right bank, while the P. melinostoma is on the left bank.

Taxon discussion
The new species can be easily distinguished from P. pupinella, P. anocamptus, P. chrysalis, P. latilabrum, P. nanpingensis, P. wenxian, P. gregorii, P. porrectus, P. himalayanus, P. siniayevi and P. tukuchensis by the shell with wide and distinct radial stripes (vs.with extremely wide radial stripes nearly covering the entire post nuclear whorls in P. pupinella; without or almost without stripes in P. anocamptus, P. chrysalis, P. latilabrum, P. nanpingensis, P. wenxian, P. himalayanus, P. siniayevi and P. tukuchensis; with spiral stripes in P. gregorii and P. porrectus).It is similar with P. melinostoma, P. obrutschewi, P. pupinidius and P. streptaxis by the similar radial striped shell, but differs from them by the thinner and reddish-brown peristome (vs.thicker and white) and the not fused A-1 and A-2 (vs.fused).It is further distinguished from P. melinostoma by the thicker stripes on shell, the sub-globular and well-defined bursa copulatrix (vs.tubular and not well defined), the unexpanded diverticle (vs.expanded) and the presence of epiphallic caecum (vs.absence); from P. obrutschewi by the unpointed apex (vs.pointed); from P. pupinidius by the slightly reflexed peristome (vs.strongly reflexed); from P. streptaxis by the taller shell.

Figure 4 .
Figure 4. Environment of the type locaity and living specimens.A Ancient Cliff Roadway; B juvenile; C dormant adults; D crawling adult.