Nanhaipotamon aureomarginatum Huang & Mao & Shih 2021, n. sp.
Creators: name: Huang, Chao
name: Mao, Siying
name: Shih, Hsi-Te
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Potamidae
Nanhaipotamon
Nanhaipotamon aureomarginatum

description: Nanhaipotamon aureomarginatum n. sp.
(Figs. 4–6, 7K, L, 8C)
urn:lsid:zoobank.org:act: 441A93FB-91A0-4FF3-9945-2EE9885B81BB
Type material. Holotype: SYSBM 001807, male (37.7 × 30.7 mm), Huidong County [ca. 23.0°N, 114.7°E], Huizhou City, Guangdong Province, China, burrow in soft mud near hillstream, 100 m a.s.l., coll. C. Huang, November 2018.
Paratypes: SYSBM 001809–001812, 4 males (30.9 × 25.3 mm, 29.1 × 23.2 mm, 27.4 × 22.3 mm, 24.7 × 20.5 mm), same data as holotype; SYSBM 001808, 001813–001815, 4 females (33.9 × 28.4 mm, 29.6 × 24.9 mm, 19.24 × 16.1 mm, 13.5 × 11.1 mm), same data as holotype; NCHUZOOL 17035, male (26.5 × 21.5 mm), same data as holotype; NCHUZOOL 17036, female (25.5 × 20.8 mm), same data as holotype; AM P.105615, male (28.9 × 23.2 mm), same data as holotype; AM P.105615, female (17.9 × 15.0 mm), same data as holotype.
Diagnosis. Carapace broader than long, regions indistinct (Fig. 4). Dorsal surface generally smooth, pitted, convex, slightly rugose on anterolateral regions in smaller specimens (Fig. 4). Anterolateral margins cristate with fused granules, bent inward posteriorly (Fig.4). Posterolateral surfaces with low,oblique striae converging posteriorly; granules scattered among striae, some merged together (Fig. 4). Sub-orbital, pterygostomial regions covered with large round granules; sub-hepatic region with lines of fused smaller granules (Fig. 5A). Maxilliped III exopod reaching to proximal one-third of merus, with flagellum (Fig. 6A). G1 slender, reaching beyond suture between sternites IV/V in situ (Fig. 5D). G1 subterminal segment 2.1–2.2 × as long as terminal segment. G1 terminal segment large, duck head-shaped; mesial margin strongly convex; outer margin strongly concave; anterior margin almost straight, oblique to longitudinal axis of G1; apex pointing outwards (Figs. 6C–E, 7K, L). G2 subterminal segment 1.7–1.8 × as long as flagellum-like terminal segment (Fig. 6B).
Description. Carapace broader than long, width 1.2–1.3 × length (n = 13), regions indistinct (Fig. 1). Dorsal surface generally smooth, pitted, convex, slightly rugose on anterolateral regions in smaller specimens (Fig. 4). Front deflexed, margin slightly ridged in dorsal view (Fig. 4). Epigastric cristae low, separated by a narrow gap (Fig. 4). Postorbital cristae prominent, laterally extended, almost fused with epigastric cristae and epibranchial teeth (Fig. 4). Branchial regions inflated; cervical grooves shallow; mesogastric region convex (Fig. 4). External orbital teeth blunt, triangular with gently convex outer margins, each separated from anterolateral margin by small gap (Figs. 4, 5A). Epibranchial teeth small, granular (Figs. 4, 5A). Anterolateral margins cristate with fused granules, bent inward posteriorly (Fig. 4). Posterolateral surfaces with low, oblique striae converging posteriorly; granules scattered among striae, some merged together (Fig. 4). Orbits large; supraorbital and infraorbital margins cristate (Figs. 4, 5A). Sub-orbital, pterygostomial regions covered with large round granules; sub-hepatic region with lines of fused smaller granules (Fig. 5A). Epistome median lobe broadly triangular, lateral margins sinuous (Fig. 5A).
Maxilliped III with merus subtrapezoidal, about as wide as long, median depression distinct; ischium; ischium subtrapezoidal, width about 0.7 × length with distinct median sulcus, with anterior mesial margin rounded; exopod reaching to proximal one-third of merus, with flagellum (Fig. 6A).
Chelipeds (pereiopod I) unequal, relatively less inflated in females (Figs. 4, 6F–I). Merus trigonal in cross section, margins lined with granules, outer-dorsal surface rugose (Figs. 4, 5A). Carpus with long, acute spine at inner-distal angle, spinule at base, dorsal surface rugose (Fig. 4). Major cheliped palm length about 1.3–1.4 × height in males (n = 6), 1.4 × in females (n = 3); dactylus about 1.0–1.1 × palm length in both males (n = 6) and females (n = 3) (Fig. 6F–I). Palm surface pitted, dorsal surface rugose. Dactylus as long as pollex. Occlusal margin of fingers lined with irregular blunt teeth, slight gape when finger tips in contact (Fig. 6F–I).
Ambulatory legs (pereiopods II–V) slender, with short and sparse setae. Pereiopods III merus 0.7 × carapace length in males (n = 6), 0.6–0.7 × in females (n = 3). Pereiopods V propodus 2.0–2.4 × as long as broad in males (n = 6), 2.2–2.3 × in females (n = 3) (Fig. 4).
Male thoracic sternum generally smooth, pitted; sternites I–IV relatively narrow, width 1.4 × as length (Fig. 5B, C). Sternites I, II fused, appearing broadly triangular; sternites II, III separated by shallow transverse sulcus, reaching edge of sternum; sternites III, IV fused, with barely visible demarcation (Fig. 5B, C). Male sterno-pleonal cavity reaching anteriorly to level of mid-length of cheliped coxa (Fig. 5B–D); median longitudinal groove separating sternites VII, VIII deep (Fig. 5D). Male pleonal locking tubercles positioned at mid-length of sternites V (Fig. 5D). Adult female vulvae ovate, relatively large but not reaching sternites V or VII; positioned closely to one another, orientation oblique to longitudinal axis of sterno-pleonal cavity (Fig. 5F).
Pleon and telson triangular in males (Fig. 5C) and broadly ovate in females (Fig. 5E). Male pleonites III–VI progressively narrower, lateral margins nearly straight; pleonite VI 1.9 × as broad as long. Male telson 1.2 × as broad as long, with blunt apex (Fig. 5C).
G1 slender, reaching beyond suture between sternites IV/V in situ (Fig. 5D). G1 subterminal segment 2.1–2.2 × as long as terminal segment (n = 3). G1 terminal segment large, duck head-shaped; mesial margin strongly convex; outer margin strongly concave; anterior margin almost straight, oblique to longitudinal axis of G1; apex pointing outwards (Figs. 6C–E, 7K, L). G2 subterminal segment 1.7–1.8 × as long as flagellum-like terminal segment (n = 3) (Fig. 6B).
Etymology. The specific name “ aureomarginatum ” alludes to the new species’ golden-coloured anterolateral margins of the carapace. The name thus is to be conceived as an adjective in the nominative singular.
Colour in life. Colour variable. Carapace generally brown to dark purple; anterolateral margins, orbital margins, and granules and striae on frontal and lateral regions of carapace golden to bright orange. Ambulatory legs olive yellow to dark purple. Chelipeds light bluish grey to orange. Juveniles usually completely brown.
Habitat. Nanhaipotamon aureomarginatum n. sp. is a lowland semi-terrestrial species found at around 100 m a.s.l. While it is sympatric with Nanhaipotamon aff. hongkongense at the type locality, the two species seem to be ecologically distinct. The smaller sized N. aff. hongkongense digs in the gravelly soil at the water’s edge next to the larger and fast flowing streams, whereas N. aureomarginatum n. sp. is more terrestrial and prefers to burrow in soft mud near the smaller branches of the hillstream or seeps.
Remarks. The overall intraspecific morphological variation is low. The general shape of the G 1 in N. aureomarginatum n. sp. seems to be quite stable (Fig. 6C–E). While externally a typical Nanhaipotamon, the proportionately large G1 terminal segment of N. aureomarginatum n. sp. (Figs. 6C–E, 7K, L) is unique amongst all congeners, with only the exceptions of N. macau and N. wupingense (Figs. 3C–E, 7I, J; Huang et al. 2018 b). Nanhaipotamon aureomarginatum n. sp. can be nevertheless differentiated from the latter two species by the higher and rounded inner distal margin of the G1 terminal segment (Fig. 6C–E, 7K, L) [vs. G1 terminal segment with inner distal margin lower and sinuous in N. macau (Huang et al. 2018 b: fig. 6C) and N. wupingense (Huang et al. 2018 b: fig. 6D)]. In the field, the new species can easily be separated with the sympatric N. aff. hongkongense by the live colouration (see “colour in life”; Fig. 8C) (vs. dark red to red in N. aff. hongkongense; Fig. 8D).
Conservation status. Nanhaipotamon aureomarginatum n. sp. is likely highly endemic. Its bright colours make it a prime target for collection for the pet trade. With this consideration, we choose to remain discreet about the exact locality of the new species.
description: Published as part of Huang, Chao, Mao, Siying & Shih, Hsi-Te, 2021, Two new freshwater crab species of the genus Nanhaipotamon Bott, 1968 (Crustacea, Decapoda, Potamidae) from Huizhou, Guangdong Province, southern China, pp. 221-238 in Zootaxa 5026 (2) on pages 228-232, DOI: 10.11646/zootaxa.5026.2.4, http://zenodo.org/record/5271442