Aiyunamon vietnamicum, Ng & Tri, 2023

Ng, Peter K. L. & Tri, Ngo Van, 2023, Two new species of semiaquatic freshwater crabs of the genera Tortomon and Aiyunamon from karst forests in northern Vietnam (Crustacea: Brachyura: Potamidae), Zootaxa 5284 (2), pp. 364-376 : 372-374

publication ID	https://doi.org/ 10.11646/zootaxa.5284.2.8
publication LSID	lsid:zoobank.org:pub:770F88D2-FA38-499B-AC81-61B8BE61992F
DOI	https://doi.org/10.5281/zenodo.7923528
persistent identifier	https://treatment.plazi.org/id/039387F1-FFB4-3A07-FF2E-5893FD34FC52
treatment provided by	Plazi
scientific name	Aiyunamon vietnamicum
status	sp. nov.

Treatment

Aiyunamon vietnamicum View in CoL n. sp.

( Figs. 6–9 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 )

Type material. HOLOTYPE: male (21.5 × 17.5 mm) ( ZRC 2022.790 View Materials ), small intermittent stream at foot of karst forest, Khun Há commune, Tam Ðý ờng district, Lai Châu province, northern Vietnam, ca. 22°13’N 103°35’E, coll. local people, 6 July 2022 GoogleMaps . PARATYPES: 2 females (27.6 × 21. 2 mm, 32.8 × 25.5 mm) ( ZRC 2022.791 View Materials ), same data as holotype GoogleMaps .

Diagnosis. Dorsal surface of carapace (especially branchial regions) gently convex in frontal view ( Fig. 7D View FIGURE 7 ); epigastric cristae rugose, not sharp, not prominently raised ( Figs. 7B View FIGURE 7 , 8A View FIGURE 8 ); postorbital cristae not sharp, rugosities relatively low, distinctly sloping posteriorly ( Figs. 7B View FIGURE 7 , 8A View FIGURE 8 ); epibranchial tooth low, just visible, separated from rest of anterolateral margin by low cleft ( Figs. 7B View FIGURE 7 , 8A View FIGURE 8 ); median lobe of posterior margin of epistome relatively wide ( Fig. 6E View FIGURE 6 ). Male pleon relatively narrow ( Fig. 8B, C View FIGURE 8 ). G1 relatively long, slender, concavity on outer margin at junction of terminal and subterminal segments relatively wide, terminal segment long, prominently curved, with low dorsal flap visible in dorsal view, tapering to relatively sharp point ( Fig. 9A–C View FIGURE 9 ). Vulva relatively large, subovate, on proximal half of sternite 6, without raised vulvar cover ( Fig. 8G View FIGURE 8 ).

Females. The two paratype females are larger than the holotype male, with their carapace proportionately wider. The epigastric and postorbital cristae are relatively lower and less prominent than that on the male but similar in form. The vulvae are relatively large ( Fig. 8G View FIGURE 8 ) and agree with the form described for congeners by Pan et al. (2022, 2023).

Colour. Dorsal surface of carapace brownish-black overall; ventral surface orangish with patches of yellow; chelae orange ( Fig. 6 View FIGURE 6 ).

Etymology. The species is named after Vietnam.

Remarks. The G1 with the curved terminal segment allies A. vietnamicum n. sp. most closely with A. tengchongense ( Dai & Chen, 1985) described from Yunnan, China (see also Dai 1999). Aiyunamon vietnamicum n. sp., however, can easily be separated by the dorsal surface of the carapace (especially the branchial regions) being gently convex ( Fig. 7D View FIGURE 7 ) (versus more convex, appearing more inflated in A. tengchongense ; Pan et al. 2020: fig. 3C); the epigastric cristae are relatively lower ( Figs. 7B View FIGURE 7 , 8A View FIGURE 8 ) (versus more swollen, distinct in A. tengchongense ; Pan et al. 2020: fig. 2C); the postorbital rugosities are relatively lower and sloping posteriorly ( Figs. 7B View FIGURE 7 , 8A View FIGURE 8 ) (versus more prominent and subparallel with the frontal margin in A. tengchongense ; Pan et al. 2020: fig. 2C); the median lobe of the posterior margin of the epistome is proportionately wider ( Fig. 7E View FIGURE 7 ) (versus median lobe of posterior margin of epistome more acutely triangular in A. tengchongense ; Pan et al. 2020: fig. 3C); the male pleon is relatively less narrower ( Fig. 8B, C View FIGURE 8 ) than in A. tengchongense (Pan et al. 2020: fig. 4C); and the concavity on the outer margin of the G1 is relatively wider with the terminal segment proportionately longer and prominently curved ( Fig. 9A–C View FIGURE 9 ) (versus shorter concavity on the outer margin of the G1 with the terminal segment proportionately shorter and only slightly curved in A. tengchongense ; Pan et al. 2020: fig. 5C, H).