Rhombuniopsis songmeng Xiang, He & Zhang, 2024

Xiang, Hong Quan, He, Yue Ming, Zhang, Le Jia, Gao, Han, Guo, Liang, Lu, Yi Zhi, Fan, Shu Yun & Chen, Hui, 2024, A revision of Rhombuniopsis Haas, 1920 (Unionida, Unionidae) endemic to the ancient lakes of Yunnan, China, with descriptions of two new species, Zootaxa 5481 (2), pp. 273-289 : 285

Rhombuniopsis songmeng Xiang, He & Zhang sp. nov.

Fig. 9A–F

Etymology: Derived from ‘Songmeng (ẇDz)’, the old name of present Songming County, where its type locality (Lake Babuhai) is located. The recommended Chinese name of this species is “ ẇDzmṉü ” (Pseudomonas aeruginosa).

Material examined. Holotype: Length 46.3 mm, from Lake Babuhai , Yanglin town (êūDz), Songming County, Kunming, Yunnan Province, China, 25.277047°N, 103.093158°E, 2021.6., collected by Hong Quan Xiang ( KIZ1904601 ) (Fig. 10 A).

Paratypes: 10 specimens ( KIZ1904602 – KIZ1904611 ): KIZ1904602–KIZ1904611, Lake Babuhai , Yanglin town, 25.277047°N, 103.093158°E, 2021.6., collected by Hong Quan Xiang.

Other-localities : Lake Lulianghai , Zhongshu Town (中NJDz), Luliang County, 25.01131°N, 103.66032°E, 2023.9.1. ( KIZ1904612 – KIZ1904614 ), collected by Hong Quan Xiang.

Diagnosis. Shell ovate, periostracum dark brown to black, pseudocardinal tooth of the right valve with a thin groove at the top.

Description. Shell(Fig. 10A–F). Length 18–60 mm. Shell small, solid, of medium thickness, ovate, symmetrical; posterior margin ovate, ventral margin straight; the umbo with wavy wrinkles, often eroded; lateral teeth long; the left valve with two pseudocardinal teeth, divided to two opposite triangles by a slit, pseudocardinal tooth of the left valve with a thin groove at the top, connected to lateral teeth; ligament long; anterior adductor muscle scar deep, posterior adductor muscle scar relatively small. Periostracum shining black; nacre white, with non-obvious fine lines.

Comparison. This species can be differentiated from the most similar species R. tauriformis by having a relatively narrow shell, weak lines on the nacre, and a more backward umbo position.

Habitat and distribution: Extinct species that inhabited muddy to sandy substrates near tributary mouths of Lake Babuhai.

Figures

FIGURE 9. Shell of Rhombuniopsis songmeng sp. nov. A. Holotype collected from Lake Babuhai, KIZ1904601, shell length 46.3 mm. B–D. Specimens collected from Lake Babuhai, KIZ1904602–KIZ1904604, shell length 45.3 mm, 40.0 mm, and 33.2 mm. E–F. Specimens collected from Lake Lulianghai, KIZ1904612–KIZ1904613, shell length 58.0 mm and 62.0 mm. Scale bars: 1 cm.