Xingyuan zhihehongi Xiang, He, Li & Chen, 2025

Xiang, Hong Quan, Lu, Yi Zhi, He, Yue Ming, Li, Chong Ye, Gao, Han, Lv, Ang Song & Chen, Hui, 2025, Twenty-seven new species and four new genera of Gastropoda (Animalia: Mollusca) from plateau lake Quaternary sediments in Yunnan, southwestern China, Ecologica Montenegrina 84, pp. 48-71 : 68-71

publication ID	https://doi.org/10.37828/em.2025.84.6
publication LSID	lsid:zoobank.org:pub:FCB98FB1-F97C-45AB-BFDF-E107D846C44D
persistent identifier	https://treatment.plazi.org/id/042F8A2D-2116-FFA6-A6AF-F956FC088F7C
treatment provided by	Felipe
scientific name	Xingyuan zhihehongi Xiang, He, Li & Chen
status	gen. et sp. nov.

Treatment

Xingyuan zhihehongi Xiang, He, Li & Chen View in CoL , gen. et sp. nov.

https://zoobank.org/ urn:lsid:zoobank.org:act:FA62BAD1-B875-491C-9D50-6975DC2F75EB

Fig. 2 View Figure 2 ZA, Fig. 11 View Figure 11 C-D

Material examined. Holotype. shell length: 3.01 mm. China, Yunnan, Yuxi County, Lake Fuxian , Lu Chong. 24.5669°N, 102.8411°E, collected by Hong Quan Xiang and Yue Ming He, January 2025. NCUBJ24301 . GoogleMaps

Paratypes. One shells, NCUBJ24203 , shell length: 3.83 mm, locality and habitat same as holotype, collected by Hong Quan Xiang and Yue Ming He, January 2025 .

Diagnosis. Shell thin, patelliform; apex prominent, curves rolled; a boundary between protoconch and teleoconch; inner lip reflexed, next to the teleoconch.

Description. Shell thin, off-white, patelliform; apex little prominent, blunt, curves downwards to the right and rolled, surpassing the right edge of shell; inner lip reflexed, next to the teleoconch. Aperture longer than wide. Teleoconch with concentric growth lines, some individuals with weak and less radial wrinkles.

Differential diagnosis. Compared to Xingyuan jiamingzhangi gen. et sp. nov., Xingyuan zhihehongi gen. et sp. nov. lacks a boundary between the protoconch and teleoconch, has a reflexed inner lip next to the teleoconch, and its apex is less prominent than the former. Additionally, the shell is wider. Although only a few complete shells were excavated during this research, the numerous shell fragments found in the strata suggest that the shell shapes of these two species are stable, with no intermediate transitional form. Therefore, this study concludes that X. zhangjiamingi gen. et sp. nov. and X. hongzhihei gen. et sp. nov. are distinct separate species.

Etymology. The species name "zhihehongi " is derived from the name of Zhi-He Hong a friend who assisted with the investigation. We suggest the Chinese common name as " 洪氏wāDz ".

Distribution and ecology. This species, along with Xingyuan jiamingzhangi gen. et sp. nov., is buried in sediment layers rich in Quaternary lake deposits. It has only been found at the type locality, and no living specimens with a similar morphology have been discovered in surveys of various lake regions.

Discussion

The survey of several ancient dry lakes in Yunnan has revealed an astonishing diversity of freshwater snails in ancient plateau lakes sediment, particularly within the family Pomatiopsidae . This represents the first comprehensive record of Pomatiopsidae subfossil (or empty shell) in Quaternary in Yunnan, China. The Pomatiopsidae species that once populated these ancient lakebeds, were distinguished by their unusually large shell sizes for the family, with some individuals exceeding 2 cm, making them the largest Pomatiopsidae species in the world. Unfortunately, due to prolonged drought and anthropogenic impacts affecting these ancient lakes, these species are now extinct. The study also investigated the surrounding water bodies, such as reservoirs, ponds, springs, and rivers, but no living individuals were found. Previously, Lake Dianchi also supported a few large living Pomatiopsidae species, including Paraprososthenia costata (Tchang & Tsi, 1949) and Paraprososthenia constricta (Tchang & Tsi, 1949) . However, due to pollution, no living specimens have been recorded in Lake Dianchi since 2000 (Du et al. 2011). Despite Lake Fuxian's large size and depth, its high elevation results in hypoxic conditions in the water. Recent climate changes and anthropogenic nutrient enrichment have further exacerbated the reduction in oxygen levels (Zhang et al. 2023). As other lakes in Yunnan, anthropogenic pollution and tourism development have severely impacted the populations of many freshwater species ( Gong et al. 2009; Du et al. 2011; Xiang et al. 2024; Zhong 2019). Strict treatment of industrial and domestic wastewater discharge around lake peripheries, enhanced protection of remaining reed wetlands (our field investigations revealed significant degradation of reed beds in Lake Fuxian), and systematic biodiversity surveys to monitor the population dynamics and conservation status of all resident species are necessary for the preservation of these unique aquatic ecosystems and their ancient biological heritage in the extant lakes.

The survey reveals consistent genus-level compositional similarities among these ancient lakes (Lake Lulianghai, Qujing Basin, Lake Yangzonghai, Lake Babuhai, Lake Fuxianhu, Lake Xingyunhu and Lake Dianchi) in Yunnan Province, as these lakes share species from one or more of the four genera that Paraprososthenia , Jullienia , Fenouilia , and Kunmingia Davis & Kuo, 1984 . This similarity is valuable for studying how the Pomatiopsidae species are dispersed within Yunnan Province. For the Lake Lulianghai, in total of 11 species across six genera within the family Pomatiopsidae were discovered during this study. This further substantiates that the recorded freshwater gastropoda fauna of the Lake Lulianghai likely represents an extinct Quaternary lake fauna, indicating that area was once a diversity hotspot with the highest rate of freshwater mollusks extictions, similar to the findings of Zhang & Wang (2023). In Qujing Basin (Qilin District, Qujing City), a total of nine Pomatiopsidae species from four genera were recorded, representing the first documented occurrence of this family in the region. Additionally, species from the genus Tchangmargarya He, 2013 of the family Viviparidae were also present in the basin. This strongly suggests the presence of an extensive paleolake system in the basin during the Quaternary period. For the investigation in Lake Yangzonghai, this is the first systematic of gastropod in soil samples from boreholes around this region. Notably, our analyses have identified only Pomatiopsidae specimens, with no other taxa detected in the Quaternary deposits. These species obtained from the boreholes have very unique morphological characteristics compare to extant Pomatiopsidae species in the lake ( Zhang et al. 1997). Additionally, an investigation of soil left from construction sites excavations near Lake Yangzonghai revealed some subfossil shells similar to those found in the boreholes. This study reveals a significant biological extinction event in history, which may have considerably reduced the diversity of Pomatiopsidae species. Therefore, further extensive research is essential to investigate the paleo-environmental changes that have impacted Pomatiopsidae species in Yangzonghai. For Lake Babuhai, this study discovered many Pomatiopsidae species buried alongside Tchangmargarya ziyi Zhang, 2017 . The study also examined lakes harboring extant populations of Tchangmargarya multilabiata Zhang & Chen, 2015 , but no Pomatiopsidae specimens were recovered. Since a large number of subfossils and empty shells have been found only in these lake deposits and not in the riverbeds, it is most likely that these species were initially originated in an ancient lake and later spread to other ancient lakes where they further evolved. It is noteworthy that no Pomatiopsidae species have been discovered among the Tertiary gastropod fossils from Qujing ( Yen, 1935). The origins and evolutionary dispersion of these large Pomatiopsidae species remain unclear, necessitating extensive further research to gain a better understanding of them.

Acknowledgements

We would like to thank the editor, Vladimir Pešić, and reviewer, Jozef Grego, for their valuable comments and suggestions, which greatly contributed to improving the manuscript.

Competing interests

The authors declare that they have no competing interests.

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Kingdom	Animalia
Phylum	Mollusca
Class	Gastropoda
Family	Lymnaeidae
Genus	Xingyuan