Tiwaripotamon xiurenense Dai & Naiyanetr, 1994

Ng, Peter K. L., 2024, Taxonomic notes on three species of Tiwaripotamon Bott, 1970 (Crustacea: Brachyura: Potamidae) from Vietnam and China, one of which is new to science, Zootaxa 5476 (1), pp. 298-313 : 308-309

publication ID

https://doi.org/ 10.11646/zootaxa.5476.1.24

publication LSID

lsid:zoobank.org:pub:880763E8-5AE7-4F9C-AB40-EC5FC386E052

DOI

https://doi.org/10.5281/zenodo.12681376

persistent identifier

https://treatment.plazi.org/id/03A2321E-FFAC-FF8F-FBBD-6044FF621761

treatment provided by

Plazi

scientific name

Tiwaripotamon xiurenense Dai & Naiyanetr, 1994
status

 

Tiwaripotamon xiurenense Dai & Naiyanetr, 1994 View in CoL

( Figs. 9–12 View FIGURE 9 View FIGURE 10 View FIGURE 11 View FIGURE 12 )

Material examined. Holotype: male (48.6 × 34.1 mm) ( ZRC 2020.169 View Materials ), Xiuren County, Guangxi Zhuang Autonomous Region , China, coll. 15 February 1938 . Paratype: 1 female (29.7 × 23.1 mm) ( CAS-CB 5197 ), same data as holotype. Others : 1 male (39.7 × 29.5 mm) (NCHUZOOL 18610), Lipu , Guangxi, southern China, coll. 18 May 2009 .

Diagnosis. Carapace subquadrate, distinctly wider than long ( Figs. 9A, B View FIGURE 9 , 10A View FIGURE 10 ); epigastric cristae very low, postorbital cristae not visible ( Figs. 9A, B View FIGURE 9 , 10A View FIGURE 10 ); external orbital tooth acutely triangular, distinct, outer margin gently convex to distinctly concave, separated from anterolateral margin by cleft ( Figs. 9A, B View FIGURE 9 , 10A View FIGURE 10 ); epibranchial tooth small sharp, rest of anterolateral margin subcristate, almost smooth, entire ( Figs. 9A, B View FIGURE 9 , 10A View FIGURE 10 ); suborbital margin convex, smooth, without inner tooth; suborbital region smooth, subhepatic, pterygostomial and sub-branchial regions weakly rugose to smooth ( Figs. 10F, H View FIGURE 10 ); posterior margin of epistome with low, wide median lobe, broadly triangular ( Fig. 10B, H View FIGURE 10 ). Male thoracic sternites punctate ( Figs. 10F View FIGURE 10 ); tubercle of male pleonal locking mechanism on posterior third of somite 5 ( Dai 1999: fig. 185-3). Ambulatory legs very long ( Figs. 9 View FIGURE 9 , 11B, C View FIGURE 11 ). Male pleon is quadrate, somites 3 and 4 very wide ( Fig. 10F, G View FIGURE 10 ). G1 with subterminal segment gently curved outwards, outer margin gently concave; terminal segment long, sharply tapering, distinctly upcurved, basal part with low rounded lobe ( Figs. 12A–F View FIGURE 12 ). Vulva large, ovate, opening subtriangular, directed obliquely inwards, occupying most of sternite 6, gently pressing onto the suture with sternite 5 ( Fig. 11D View FIGURE 11 ).

Females and variation. The female paratype is smaller than the holotype male and the carapace is quite different in appearance. Compared to the male ( Fig. 9A View FIGURE 9 ), its carapace is distinctly more quadrate, proportionally narrower with the branchial regions less swollen, the external orbital tooth is less acute with the outer margin gently convex and the epibranchial tooth is not sharp ( Fig. 9B View FIGURE 9 ). As with most potamids, the female chelae are relatively smaller and the major chela is not inflated and enlarged ( Fig. 9B View FIGURE 9 versus Figs. 9A View FIGURE 9 , 11A View FIGURE 11 ).

Remarks. Among the many specimens of Chinese crabs donated to the ZRC in the 1990s as part of an exchange of material with the late Prof Dai Ai-Yun was a specimen of Tiwaripotamon xiurenense . It was not labelled as a type and has been placed in the main shelves of the ZRC since the exchange. A re-examination of this specimen shows that it is actually the holotype male described and figured by Dai & Naiyanetr (1994), agreeing in all details, including the measurements. It is here re-catalogued as the holotype of the species. This also explains why Ng Ngan Kee, Zhou Xianmin and Tohru Naruse could not locate the holotype of the species when they photographed the types of freshwater crabs in CAS; and only the paratype female was found ( Fig. 9B View FIGURE 9 ).

A smaller male (39.7 × 29.5 mm, NCHUZOOL 18610), collected from Lipu in Guangxi, is also here identified with T. xiurenense ; its carapace features and G1 structure agree very well with the holotype male.

It is important to note that the G1 as depicted in the original figure of the species ( Dai & Naiyanetr 1994: fig. 2-4, 2-5; Dai 1999: fig. 185-4, 185-5) is drawn tilted to one side. In these figures, the G1 subterminal segment is slender, the terminal segment is very long and slender, and there is a small basal dorsal flap visible in the ventral and dorsal views (see Fig. 12B, E View FIGURE 12 ). When the G1 is viewed with the lateral surfaces horizontal and centred (standard orientation for freshwater crab figures), however, the structure looks very different, with the subterminal segment much wider, the terminal segment is relatively shorter and the basal dorsal flap is not visible in the ventral or dorsal views ( Fig. 12A, C, D, F View FIGURE 12 ). The very different appearance of the G1 when figured from different perspectives is a factor that must be considered when comparisons with allied taxa are made. Previous papers describing species of Tiwaripotamon have relied primarily on the original figures by Dai & Naiyanetr (1994) and Dai (1999) for T. xiurenense and T. pingguoense , so these comparisons are not completely reliable (e.g., Yeo & Ng 2001; Do et al. 2017).

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