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 299961 10.11646/zootaxa.5481.2.6 63169ed8-3950-427d-b067-015c6823bf03 1175-5326 12749748 80194D39-74AD-4C40-AAAC-C2F52D4FF179 Rhombuniopsis tauriformis Fulton, 1906 Fig. 4 A–F Unio (Cuneopsis) tauriformis Fulton (1906) : 246 , pl. 9, fig. 9 [‘ Yunnan fu’ = Kunming, Yunnan Province , China ]. Cuneopsis tauriformis Simpson (1914) : 948 –949. Rhombuniopsis tauriformis Haas (1920) : 146 –151; Haas (1924): 185; Thiele (1934): 779–1022; Haas (1969): 269–270; Du et al. (2011) : 216 ; He & Zhuang (2013) : 100 , Figs 235–236; Zieritz, Bogan, Froufe et al. (2018) : 29 –44; Graf & Cummings (2021) : 15 ; Liu, Liu, Wu et al. (2022) : 1–37 . Rhombuniopsis cuneopiformis Huang & Zhang (1990) : 69 –75; Du et al. (2011) : 216. Material examined. Newly collected material. Adult shell: Lake Dianchi , Shangsuan Town ( 上ũDz ), 24.695185°N , 102.689200°E , 2017.11. ( KIZ1904101 – KIZ1904103 ), collected by Jiao Wei Ning and Hong Quan Xiang ; Lake Dianchi , Xiaoqinghe Village ( 小DZāñ ), 24.695185°N , 102.689200°E , 2019.6. ( KIZ1904104 – KIZ1904105 ), collected by Liang Guo ; Lake Dianchi , Haikou ( DZ口 ), 24.78012°N , 102.62258°E , 2023.5. ( KIZ1904106 – KIZ1904110 ), collected by Hong Quan Xiang ; Lake Lulianghai , Zhongshu Town ( 中NJDz ), Luliang County , 25.01131°N , 103.66032°E , 2023.9.1 . ( KIZ1904111 – KIZ1904113 ), collected by Hong Quan Xiang . Diagnosis. Shell ovate to triangulate ovate, dark brown to black; umbo near to the front, with wavy wrinkles. Description. Shell ( Fig. 4 A–F ). Length 20–55 mm . Shell small, thick, obliquely ovate, symmetrical or slightly asymmetrical, wedge-shaped, anterior margin truncate, posterior margin sharp or round; periostracum shining black, the umbo sculptured with wavy wrinkles, often eroded. Anterior adductor muscle scar oval, very deep; posterior adductor muscle scar round to oval, shallow. Left valve with two pseudocardinal teeth, anterior tooth rather thin, posterior tooth thick; anterior pseudocardinal tooth of the right valve well developed, spherical; lateral teeth long and thick; nacre white. FIGURE 4. Shells of Rhombuniopsis tauriformis . A. Specimen collected from Lake Dianchi, KIZ1904101, shell length 37.2 mm. B. Specimen collected from Lake Dianchi, KIZ1904102, shell length 25.0 mm. C. Specimen collected from Lake Dianchi, KIZ1904104, shell length 37.0 mm. D. Holotype of R. tauriformis , fu-Yunnan, Yunnan (NHMUK 1906.5.8.72). E. Specimen collected from Lake Lulianghai, KIZ1904111, shell length 46.0 mm. F. Specimen collected from Lake Lulianghai, KIZ1904112, shell length 43.0 mm. Scale bars: 1 cm. Comparison. This species can be differentiated from the most similar species R. songmeng sp. nov. by having a relatively prominent umbo and an obliquely ovoid shell. Taxonomic remarks. Fulton (1906) described Unio (Cuneopsis) tauriformis based on shells collected from Kunming. According to the morphology of its shell, Haas (1920) assigned this species to Rhombuniopsis . Huang & Zhang (1990) described a new species, Rhombuniopsis cuneopiformis from shells collected at Lake Dianchi, but our morphological comparison confirms that it should be a synonym of R. tauriformis . Habitat and distribution. Lives on muddy to sandy substrates, mostly found along the shores of lakes and where rivers enter the lakes at depths of 0–3 m . Known to occur in the Dianchi and Lulianghai lakes.