A revision of Rhombuniopsis Haas, 1920 (Unionida, Unionidae) endemic to the ancient lakes of Yunnan, China, with descriptions of two new species Author Xiang, Hong Quan Yuxi Agriculture Vocation-Technical College Department of Animal Science. Yuxi 653106, China Author He, Yue Ming College of Engineering and Technology, Tianjin Agricultural University, Tianjin 300384, China Author Zhang, Le Jia Museum für Naturkunde, Leibniz, Institut für Evolutions und Biodiversitätsforschung, Berlin 10115, Germany Author Gao, Han Fuzhou University College of Computer and Data Science / College of Software, Fuzhou 350108, China Author Guo, Liang Fuzhou Wilds of Insects Cultural Creativity Co., Ltd., Fuzhou 350025, China Author Lu, Yi Zhi Auburn University, Auburn, AL 36849, Alabama, United States of America Author Fan, Shu Yun Kunming Institute of Fishery Sciences, Kunming 650021, China Author Chen, Hui Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China text Zootaxa 2024 2024-07-16 5481 2 273 289 http://dx.doi.org/10.11646/zootaxa.5481.2.6 journal article 10.11646/zootaxa.5481.2.6 1175-5326 12749748 80194D39-74AD-4C40-AAAC-C2F52D4FF179 Rhombuniopsis fultoni Moskvicheva & Starobogatov, 1973 Fig. 5A–D Rhombuniopsis fultoni Moskvicheva & Starobogatov (1973) : 24 , fig. 2 [‘ Yunnan fu’=Kunming, Yunnan Province , China ]; Graf & Cummings (2007) : 304 ; He & Zhuang (2013) : 102 , Figs 239–240; Zieritz et al. (2018) : 29 –44; Graf & Cummings (2021) : 15 ; Liu et al. (2022) : 1 –37. Material examined. Newly collected material. Adult shell: Lake Lulianghai , Zhongshu Town ( 中NJDz ), 25.028233°N , 103.689557°E , 2022.1. ( KIZ1904201 – KIZ1904210 ), collected by Hong Quan Xiang and Yue Ming He; Lake Dianchi , Haikou ( DZ口 ), 24.782123°N , 102.610330°E , 2022.1. ( KIZ1904211 ), collected by Yi Feng Liu ; Lake Dianchi , Haikou ( DZ口 ), 24.78012°N , 102.62258°E , 2023.5. ( KIZ1904212 – KIZ1904217 ), collected by Hong Quan Xiang. FIGURE 5. Shells of Rhombuniopsis fultoni . A–B. Specimens collected from Lake Lulianghai, KIZ1904201–KIZ1904202, shell length 33.0 mm and 36.3 mm. C. Specimen collected from Lake Dianchi, KIZ1904211, shell length 26.0 mm. D. Holotype of R. fultoni , collected from Kunming, Yunnan, shell length 32.0 mm (from Moskvicheva & Starobogatov, 1973 ). Scale bars: 1 cm. Diagnosis. Shell rounded or nearly rounded, dark brown to black, ventral margin rounded, umbo with wavy wrinkles. Description. Shell length 20–25 mm . Shell small, inflated, solid, symmetrical, rounded or nearly rounded. Anterior and posterior margins oval, ventral margin rounded; the umbo sometimes sculptured with wavy wrinkles, often eroded. Ligament short; growth lines arranged in concentric circles; dorsal outline arched smoothly. Periostracum shining black or greenish-yellow, smooth; left valve with two pseudocardinal teeth, anterior tooth rather thin, posterior tooth thick; anterior pseudocardinal tooth of the right valve well developed, spherical, posterior tooth sometimes connected to lateral teeth; nacre white. Comparison. This species can be differentiated from the most similar species R. linan sp. nov. by having a rounder shell with relatively smaller pseudocardinal teeth and fewer wavy wrinkles near the umbo. Taxonomic remarks. According to Moskvicheva and Starobogatov (1973) , Rhombuniopsis fultoni was described based on shells collected from Yunnan ( type locality: Kunming, China ). He and Zhuang (2013) provided specimen images from Lake Dianchi in Kunming. Based on comparative descriptions, we believe they represent the same species. Huang & Zhang (1990) described a new species found in Dianchi, Unionea ovatiquadreta ( Huang & Zhang, 1990 ) . However, after searching for Huang & Zhang’s information from the relevant years, we could not find any images of that species. Other references citing this species also did not provide any relevant literature. We consider this species to be invalid. Therefore, we can only speculate that it is R. fultoni based on the shape described in its name and its place of origin. In addition, Huang & Zhang (1990) recorded ‘ Unionea fagana ’ from Dianchi. According to our research, this name should actually be a misspelling of Unionetta fabagina ( Deshayes & Jullien, 1876 ) . Based on our field investigations in Dianchi, we believe that Huang & Zhang’s identification was wrong, and this species should actually be R. fultoni . Habitat and distribution. Lives on muddy to sandy substrates, mostly found near rivers leading to lakes, always at depths of 0–3 m in Lake Dianchi, Lulianghai and lakes near Qujing City.