Huananpotamon amicitiae Wang, Pan & Sun, 2024, sp. nov.
Creators: name: Wang, Ruxiao
name: Pan, Da
name: Sun, Hongying
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Potamidae
Huananpotamon
Huananpotamon amicitiae

description: Huananpotamon amicitiae sp. nov.
(Figs. 2–3, 4A–E, 5A–B, 6A)
Type material. Holotype: NNU 16C-220815HA1, male (20.5× 16.5 mm), Shegeng Town, 28°24ʹ14ʹʹN, 116°41ʹ21ʹʹE, 81 m a.s.l., Yugan County, Shangrao City, Jiangxi Province, China (Fig. 1), coll. H. Chen, Y.L. Sun & D. Pan, 15 August 2022. Paratypes: NNU 16C-220815HA2–4, 3 males (16.3 × 12.8 mm, 19.6 × 16.0 mm, 13.9 × 12.0 mm), same data as holotype; NNU 16C-220815HA5–7, 3 females (16.2 × 13.2 mm, 16.2 × 13.3 mm, 14.8 × 12.2 mm), same data as holotype.
Diagnosis. Carapace broader than long, dorsal surface pitted, gently convex (Fig. 2A); frontal region deflexed downwards (Fig. 2A, B); external orbital angle triangular, sharp, separated from epibranchial tooth by distinct U-shaped notch; epibranchial teeth small but distinct (Fig. 2A). Epigastric cristae distinct, rugose, separated medially by narrow groove (Fig. 2A, B); postorbital cristae distinct, confluent with epibranchial teeth (Fig. 2A, B); postorbital region distinctly concave (Fig. 2A, B); anterolateral region convex with granules (Fig. 2A). Cervical grooves shallow (Fig. 2A); H-shaped groove distinct (Fig. 2A). Ischium of third maxilliped trapezoidal, with long and distinct median sulcus; exopod with flagellum (Fig. 3A). G1 slender, straight; tip part of terminal segment expanded, inner-distal angle very high, rounded, outer-distal angle elongated, horn-shaped, recurved in lateral view (Figs. 3B, G, 5A, B). G2 terminal segment elongated (Fig. 2D). Vulvae elongate, ovate, not reaching suture of sternites 5/6 anteriorly (Fig. 4E).
Description. Carapace broader than long, regions distinct, dorsal surface gently convex, finely pitted (Fig. 2A). Frontal margin gently sinuous, almost smooth (Fig. 2B). Epigastric cristae distinct, separated medially by groove (Fig. 2A, B); postorbital cristae sharp, distinct, separated from epigastric cristae by shallow groove, confluent with epibranchial teeth (Fig. 2A, B); postorbital region distinctly concave (Fig. 2A, B). Cervical grooves shallow (Fig. 2A); H-shaped groove distinct (Fig. 2A); Anterolateral region convex with granules (Fig. 2A); posterolateral region smooth, with oblique striae; posterolateral margins converging posteriorly (Fig. 2A). External orbital angle distinct, sharp, triangular, outer margin convex and longer than inner margin, lined with small granules (Fig. 2A). Epibranchial tooth distinct, demarcated from external orbital tooth by distinct U-shaped notch (Fig. 2A). Anterolateral margin convex, lined with low granules (Fig. 2A). Orbits ovate, large; supra- and infraorbital margins cristate, lined with numerous inconspicuous granules (Fig. 2B). Epistome posterior margin with median lobe broadly triangular, lateral margins slightly sinuous (Fig. 2B).
Third maxilliped ischium trapezoidal, length about 1.3× width, surface pitted, with distinct median oblique groove; merus subquadrate, length about 0.8× width (Fig. 3A); exopod slender, reaching proximal one-third of merus length, with flagellum (Fig. 3A).
Adult chelipeds slightly asymmetrical (Fig. 2A). Merus margins crenulate (Fig. 2A). Carpus surface gently rugose, inner margin with sharp spine, with spinule basally (Fig. 2A). Major cheliped palm length about 1.2× height, outer surface generally rugose, sparsely pitted; fingers of major cheliped slightly curved, outer surface with rows of pits; dactylus 0.94 times as long as palm length. Occlusal margin of both fingers lined with 11–13 irregular teeth, forming narrow gape when fingers closed (Fig. 3E, F).
Ambulatory legs slender, surfaces and margins with scattered short setae (Fig. 2A); second ambulatory leg longest, merus about 1.5 times as long as dactylus (Fig. 2A).
Thoracic sternum surface generally smooth, weakly pitted (Fig. 2C, D); sternites 1, 2 fused, forming triangular structure, separated from sternite 3 by conspicuous suture; sternites 3, 4 completely fused (Fig. 2C, D). Male sternopleonal cavity reaching to imaginary line connecting median part of cheliped coxae (Fig. 2C). Male pleonal locking tubercle on median part of sternite 5 (Fig. 2D).
Male pleon triangular, surface smooth (Fig. 2C); somites 3–6 gradually decreasing in width; somite 6 width about 1.8× length; telson broadly triangular, width about 1.6× length, apex rounded (Fig. 2C). Female pleon ovate; somite 6 width about 2.5× length; telson semicircular, width about 2.0× length (Fig. 4D).
G1 slender, straight (Fig. 3B, C, G); tip exceeding pleonal locking tubercles in situ, reaching suture between thoracic sternites 4/5 (Fig. 2D); subterminal segment length about 1.7× length of terminal segment; terminal segment slender, straight, distally expanded, inner-distal angle very high, rounded, outer-distal angle elongated and directed upwards in ventral view (Figs. 3B, 5A), recurved in lateral view (Fig. 5B); groove for G2 running mid-line of ventral surface (Fig. 3B). G2 subterminal segment tapering distally, about 2.1× length of elongated terminal segment (Fig. 3D). Vulvae on thoracic sternite 6, not reaching suture of sternites 5/6 anteriorly, elongate, ovate, closely spaced from one another, opening inwards (Fig. 4E).
Etymology. The name is derived from the word amicitia, Latin for friendship, to honor the precious relationship the authors have had over the decades with the recently departed Dr Ng Ngan Kee, from the National University of Singapore. She was a good friend who helped facilitate many exchanges and collaborations between our universities over the years.
Colour in life. Individuals are mottled brown overall. The chelipeds are light-yellow (Fig. 6A).
Habitat. This new species is characteristic of low-altitude hill streams, with sandy sediments under the stones (Fig. 6B).
Remarks. Huananpotamon amicitiae sp. nov. fits well with morphological descriptions of the genus, including the dorsal surface of the carapace being slightly convex, with fine rugae on the epibranchial regions, the exopod of third maxilliped possessing a well-developed flagellum, the male pleon being relatively narrow and acutely triangular in shape, the G1 is relatively long, slender, with the distal part of the subterminal segment slender, and the distal part of the terminal segment expanded to form a lobe, flap or similar projection (Dai & Ng 1994; Dai 1999). The new species, H. amicitiae sp. nov., possesses an elongated outer-distal angle of the G1 terminal segment (Figs. 3B, 5A), a distinctive character shared with nine congeners from nearby regions (Fig. 7): H. angulatum (Dai, Chen, Song, Fan, Lin & Zeng, 1979), H. chongrenense Dai, Zhou & Peng, 1995, H. guixiense Dai, Zhou & Peng, 1995, H. koatenense (Rathbun, 1904), H. lichuanense Dai, Zhou & Peng, 1995, H. lini Cheng & Li, 2008, H. medium Dai, Zhou & Peng, 1995, H. sheni Cheng & Li, 2008, H. yiyangense Dai, Zhou & Peng, 1995 (cf. Cheng et al. 2008: fig. 1(8); Dai & Ng 1994: fig. 1; Dai et al. 1995: figs. 1(4)–7(4)). The very high and well-developed inner-distal angle of the G1 terminal segment of H. amicitiae sp. nov. (Figs. 3G, 5B), however, is a distinguishing character, and is a feature shared only with H. koatenense (Fig. 5C; cf. Wang et al. 2022b: fig. 5B, C) and H. lini (Fig. 5E; cf. Cheng et al. 2008: fig. 1(7), (8)).
Huananpotamon amicitiae sp. nov. can be clearly differentiated from H. lini by the following characters: G1 reaching suture between thoracic sternites 4/5 (Fig. 2D) (versus G1 exceeding pleonal locking tubercle in situ, but not reaching suture between thoracic sternites 4/ 5 in H. lini; cf. Cheng et al. 2008: fig. 1(7)); G1 terminal segment with inner-distal angle relatively high, globular in shape (Figs. 3B, G, 5B) (versus inner-distal angle relatively low, somewhat blunt in H. lini; Fig. 5E, F; cf. Cheng et al. 2008: fig. 1(8)); G1 terminal segment with outer-distal angle more elongate (Figs. 3B, G, 5A) (versus terminal segment outer-distal angle relatively shorter in H. lini; Fig. 5E, F; cf. Cheng et al. 2008: fig. 1(8)); and G1 terminal segment with outer-distal angle strongly recurved and relatively thick in lateral view (Fig. 5B) (versus outer-distal angle slightly recurved and relatively more slender in lateral view in H. lini; Fig. 5F; cf. Cheng et al. 2008: fig. 1(7), (8)). Other more subtle differences in the external orbital angle, postorbital cristae, and vulva are listed in Table 1.
Huananpotamon koatenense was described from one female (MNHN-IU-2014-23011), which had been incorrectly placed in Sinopotamon Bott, 1967. In a previous study, we collected a series of specimens from the type locality and identified them as H. koatenense, and then the author redescribed the species and resolved its taxonomy (see Wang et al. 2022a). We compared the detailed photographs of the type specimen of H. koatenense with the female H. amicitiae sp. nov. specimens from Yugan County. Huananpotamon amicitiae sp. nov. clearly differs from H. koatenense by the external orbital tooth being acutely triangular (Fig. 4A–C) (versus external orbital tooth broadly triangular in H. koatenense; Fig. 4F–H), and the epibranchial tooth is relatively larger, more rounded, and separated from the external orbital tooth by a broadly U-shaped cleft (Fig. 4A–C) (versus epibranchial tooth relatively smaller, granular, separating from external orbital tooth by narrow V-shaped cleft in H. koatenense; Fig. 4F–H). Huananpotamon amicitiae sp. nov. can be distinguished from H. koatenense by the following characters: G1 terminal segment with inner-distal angle relatively higher, globular in shape (Figs. 3B, G, 5A, B) (versus terminal segment with inner-distal angle relatively lower, globular in shape in H. koatenense; Fig. 5C, D), and outer-distal angle strongly curved ventral-ward and relatively thin in lateral view (Fig. 5B) (versus outer-distal angle almost straight and relatively thick in lateral view in H. koatenense; Fig. 5D). Other subtle differences existing in the postorbital cristae, cleft between external orbital angle and epibranchial tooth are listed in Table 1.
description: Published as part of Wang, Ruxiao, Pan, Da & Sun, Hongying, 2024, A new species of freshwater crab of the genus Huananpotamon Dai & Ng, 1994 (Decapoda: Brachyura: Potamidae) from northern Jiangxi, China, pp. 463-473 in Zootaxa 5476 (1) on pages 465-470, DOI: 10.11646/zootaxa.5476.1.34, http://zenodo.org/record/12696581