Pseudopostolata angula Chen, Dai, Huang & Wu, 2024

Dai, Yu-Ting, Chen, Zhong-Guang, Cheng, Yu-Zhuo, Huang, Xiao-Chen, Ouyang, Shan, Shu, Feng-Yue & Wu, Xiao-Ping, 2024, Molecular phylogeny reveals a new genus and species of freshwater mussel (Bivalvia, Unionidae, Gonideinae) from Jiangxi, China, Zoosystematics and Evolution 100 (4), pp. 1419-1429 : 1419-1429

Pseudopostolata angula Chen, Dai, Huang & Wu , sp. nov.

Figs 2 C, D , 4

Material examined.

Holotype • 24 _ NCU _ XPWU _ PA 01 , Wujiang River [乌江], Yongfeng County [永丰县], Ji’an City [吉安市], Jiangxi Province [江西省], China, 27 ° 03 ' 37 " N, 115 ° 42 ' 17 " E, collected by Zhong-Guang Chen in December 2023 ; Paratypes China • 7 shells; same collection data as for holotype; specimen vouchers were shown in Table 4 .

Diagnosis.

See the diagnosis of the genus.

Description.

Shell medium size, moderately thick, flat, long, glossy. Length 52.16–84.18 mm, width 16.80–25.95 mm, height 32.40–49.53 mm (Table 4 ). Anterior rounded, short, posterior long, and wide. Dorsal margin slightly curved downwards and truncated in behind, with a distinct obtuse angle in the middle of posterior margin; ventral margin weakly curved. Umbo inflated, below or even with the hinge line, located at 1 / 3 of the dorsal margin, and often eroded. Periostracum black with thin growth lines. Posterior slope with a low secondary posterior ridge end in the angle on the posterior margin. Growth lines arranged in irregular concentric circles. Hinge long. Ligament short and strong. Beak cavities shallow, open. Mantle attachment scars on the pallial line obvious. Anterior adductor muscle scars irregularly oval, deep, rough; posterior adductor muscle scars long, oval, smooth. Anterior retractor muscle scar deep; posterior adduster muscle scar shallow, Located obliquely above posterior adductor muscle scars. Left valve with one or two pseudocardinal teeth; anterior tooth elevated pyramidal or degenerated; posterior tooth thick and pyramidal. Right valve also with one or two pseudocardinal teeth; anterior tooth small or elevated pyramidal; posterior tooth low triangular or degenerated. Lateral teeth of both valves long and thick. Nacre light orangish.

Etymology.

The specific name angula is made from the Latin angula for angled, alluding to the angle on the posterior margin of this species.

Vernacular name.

‘ Angulated pseudorear-wide mussel’ (English) and Ju Jiao Ni Hou Ju Bang (具角拟后矩蚌) (Chinese).

Distribution.

Pseudopostolata angula sp. nov. is only known from the type locality (Fig. 1 ).

Habitat.

This new species was found to occur in the muddy or pebbly substrate of the river together with Diaurora aurorea (Heude, 1883) , Lanceolaria triformis (Heude, 1877) , Lamprotula caveata (Heude, 1877) , Nodularia douglasiae (Gray, 1833) and Pseudocuneopsis yangshuoensis Wu & Liu, 2023 (Fig. 2 A, B ). It is the occasional species in the habitat, accounting for 5 % of the total density of freshwater mussels.

Figures

Figure 1. Distribution map of Pseudopostolata angula gen. et sp. nov.

Figure 2. The type locality and shell morphology of Pseudopostolata angula gen. et sp. nov. A, B. General view of the type locality, Wujiang River, Ji’an City, Jiangxi Province, China; C, D. Shell morphology of Pseudopostolata angula.

Figure 4. Eight specimens of Pseudopostolata angula gen. et sp. nov. were collected from the Wujiang River in Ji’an City, Jiangxi, China. A is the holotype; A-H responds to specimen vouchers: 24 _ NCU _ XPWU _ PA 01 - 24 _ NCU _ XPWU _ PH 08.