Aiyunamon vietnamicum Ng & Tri 2023, n. sp.
Creators: name: Ng, Peter K. L.
name: Tri, Ngo Van
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Potamidae
Aiyunamon
Aiyunamon vietnamicum

description: Aiyunamon vietnamicum n. sp.
(Figs. 6–9)
Type material. HOLOTYPE: male (21.5 × 17.5 mm) (ZRC 2022.790), 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. PARATYPES: 2 females (27.6 × 21. 2 mm, 32.8 × 25.5 mm) (ZRC 2022.791), same data as holotype.
Diagnosis. Dorsal surface of carapace (especially branchial regions) gently convex in frontal view (Fig. 7D); epigastric cristae rugose, not sharp, not prominently raised (Figs. 7B, 8A); postorbital cristae not sharp, rugosities relatively low, distinctly sloping posteriorly (Figs. 7B, 8A); epibranchial tooth low, just visible, separated from rest of anterolateral margin by low cleft (Figs. 7B, 8A); median lobe of posterior margin of epistome relatively wide (Fig. 6E). Male pleon relatively narrow (Fig. 8B, C). 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). Vulva relatively large, subovate, on proximal half of sternite 6, without raised vulvar cover (Fig. 8G).
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) 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).
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) (versus more convex, appearing more inflated in A. tengchongense; Pan et al. 2020: fig. 3C); the epigastric cristae are relatively lower (Figs. 7B, 8A) (versus more swollen, distinct in A. tengchongense; Pan et al. 2020: fig. 2C); the postorbital rugosities are relatively lower and sloping posteriorly (Figs. 7B, 8A) (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) (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) 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) (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).
Ecology. As for Tortomon distinctum n. sp.
Conservation. As for Tortomon distinctum n. sp.
description: Published as part of 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), pp. 364-376 in Zootaxa 5284 (2) on pages 372-374, DOI: 10.11646/zootaxa.5284.2.8, http://zenodo.org/record/7923530