Rhombuniopsis linan 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 : 283-284

Rhombuniopsis linan Xiang, He & Zhang sp. nov.

Fig. 8A–I

Etymology: Derived from ‘Linan (临AE)’, the ancient name of Jianshui County in Honghe Hani and Yi Autonomous Prefecture, Yunnan Province. The recommended Chinese name of this species is “ 临AEmṉü ” (Lin'an pearl clam).

Material examined. Holotype: Length 61.4 mm, from Lake Yilong , Shigang Village (ƋṄñ), 102.615266°E, 23.666839°N, 2023.4., from Hong Quan Xiang and Yue Ming He. ( KIZ1904501 )( Fig.8 A ) .

Paratypes: 10 specimens (KIZ1904502–KIZ19045011): KIZ1904502 , Lake Yilong , Lulai Village (Rẍñ), 102.596596°E, 23.655097°N, 2023.3., from Jiao Wei Ning ; KIZ1904503 , Lake Yilong , Shaba Village (Ủ坝ñ), Baxin Town, Shiping County, Yunnan Province, China, 102.628906°E, 23.658542°N, 2023.1., coll. Hong Quan Xiang. KIZ1904504 – KIZ1904511 , Lake Yilong , Shigang Village (ƋṄñ), 102.615266°E, 23.666839°N, 2023.4., from Hong Quan Xiang and Yue Ming He .

Other-location: Lake Fuxian , Yousuo Town (右ãñ), 102.908495°E, 24.631587°N, 2023.1.20.( KIZ1904512 ), from Chong Ye Li ; Lake Fuxian , 102.863819°E, 24.138159°N, 2023.7. ( KIZ1904513 ), from Chong Ye Li ; Lake Qilu , Xiushan Street (WƜĕ), Tonghai County, 102.748644°E, 24.138159°N, 2022. ( KIZ1904514 ), from Le Jia Zhang ; Lake Xingyun , Longjie Village (kĕñ), 102.806266°E, 24.385006°N, 2022.4. ( KIZ1904515 – KIZ1904516 ), from Suo Zhu Yang ; Lake Xingyun , Longjie Village, 102.806255°E, 24.385000°N, 2022.4. ( KIZ1904517 ), from Hong Quan Xiang .

Diagnosis. Shell round to ovate, periostracum dark brown to black; pseudocardinal tooth of the right valve in some individuals extend upward, the umbo with wavy wrinkles and wrinkles occur only on the umbo.

Description. Shell ( Fig. 8 A–I ). Length 20–78 mm. Shell large, round to ovate, thick, obese and inflated. Dorsal margin arched smoothly, anterior margin rounded, ventral margin slightly rounded; umbo located at 1/3 of the dorsal margin, sculptured with obvious and deep wavy wrinkles, the umbo has vertical stripes near the wrinkles, often eroded; ligament long. Lateral teeth long, the right valve with one extremely thick and raised pseudocardinal tooth, extending upward and having a groove in the upper part; the left valve with two pseudocardinal teeth, anterior tooth rather thin, posterior tooth thick. Anterior adductor muscle scar very deep, posterior adductor muscle scar relatively small; periostracum shining black or with brownish-yellow, nacre orange-yellow or white.

Comparison. This species can be differentiated from the most similar species R. fultoni by having a thick pseudocardinal tooth of the right valve, extending upward and having a groove in the upper part. The nacre of R. linan sp. nov. is sometimes orange-yellow, a color that has not been observed in other Rhombuniopsis species.

Habitat and distribution. Extinct species that inhabited muddy to sandy substrates near river mouths in Lake Yilong, Qilu, Xingyun, Fuxian.

Figures

FIGURE 8. Shell of Rhombuniopsis linan sp. nov.. A. holotype, Specimen collected from Lake Yilong, KIZ1904501, 61.4 mm. B–D. Specimen collected from Lake Yilong, KIZ1904502–KIZ1904504, 61.5 mm, 61.5 mm, 56.0 mm. E. Specimen collected from Lake Fuxian, KIZ1904512, 47.9 mm. F. Specimen collected from Lake Fuxian, KIZ1904513, 43.9 mm. G. Specimen collected from Lake Qilu, KIZ1904514. H. Specimen collected from Lake Xingyun, KIZ1904515. I. Specimen collected from Lake Xingyun, KIZ1904517. Scale bars: 1 cm.