Huananpotamon amicitiae, Wang & Pan & Sun, 2024

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, Zootaxa 5476 (1), pp. 463-473 : 465-470

publication ID	https://doi.org/ 10.11646/zootaxa.5476.1.34
publication LSID	lsid:zoobank.org:pub:35F89F45-612B-4F96-87C3-29CABB4365CD
DOI	https://doi.org/10.5281/zenodo.12696464
persistent identifier	https://treatment.plazi.org/id/03CA1626-083F-FFBD-FE95-DD2CFB72FF4A
treatment provided by	Plazi
scientific name	Huananpotamon amicitiae
status	sp. nov.

Treatment

Huananpotamon amicitiae sp. nov.

( Figs. 2–3 View FIGURE 2 View FIGURE 3 , 4A–E View FIGURE 4 , 5A–B View FIGURE 5 , 6A View FIGURE 6 )

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 View FIGURE 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 View FIGURE 2 ); frontal region deflexed downwards ( Fig. 2A, B View FIGURE 2 ); external orbital angle triangular, sharp, separated from epibranchial tooth by distinct U-shaped notch; epibranchial teeth small but distinct ( Fig. 2A View FIGURE 2 ). Epigastric cristae distinct, rugose, separated medially by narrow groove ( Fig. 2A, B View FIGURE 2 ); postorbital cristae distinct, confluent with epibranchial teeth ( Fig. 2A, B View FIGURE 2 ); postorbital region distinctly concave ( Fig. 2A, B View FIGURE 2 ); anterolateral region convex with granules ( Fig. 2A View FIGURE 2 ). Cervical grooves shallow ( Fig. 2A View FIGURE 2 ); H-shaped groove distinct ( Fig. 2A View FIGURE 2 ). Ischium of third maxilliped trapezoidal, with long and distinct median sulcus; exopod with flagellum ( Fig. 3A View FIGURE 3 ). 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 View FIGURE 3 , 5A, B View FIGURE 5 ). G2 terminal segment elongated ( Fig. 2D View FIGURE 2 ). Vulvae elongate, ovate, not reaching suture of sternites 5/6 anteriorly ( Fig. 4E View FIGURE 4 ).

Description. Carapace broader than long, regions distinct, dorsal surface gently convex, finely pitted ( Fig. 2A View FIGURE 2 ). Frontal margin gently sinuous, almost smooth ( Fig. 2B View FIGURE 2 ). Epigastric cristae distinct, separated medially by groove ( Fig. 2A, B View FIGURE 2 ); postorbital cristae sharp, distinct, separated from epigastric cristae by shallow groove, confluent with epibranchial teeth ( Fig. 2A, B View FIGURE 2 ); postorbital region distinctly concave ( Fig. 2A, B View FIGURE 2 ). Cervical grooves shallow ( Fig. 2A View FIGURE 2 ); H-shaped groove distinct ( Fig. 2A View FIGURE 2 ); Anterolateral region convex with granules ( Fig. 2A View FIGURE 2 ); posterolateral region smooth, with oblique striae; posterolateral margins converging posteriorly ( Fig. 2A View FIGURE 2 ). External orbital angle distinct, sharp, triangular, outer margin convex and longer than inner margin, lined with small granules ( Fig. 2A View FIGURE 2 ). Epibranchial tooth distinct, demarcated from external orbital tooth by distinct U-shaped notch ( Fig. 2A View FIGURE 2 ). Anterolateral margin convex, lined with low granules ( Fig. 2A View FIGURE 2 ). Orbits ovate, large; supra- and infraorbital margins cristate, lined with numerous inconspicuous granules ( Fig. 2B View FIGURE 2 ). Epistome posterior margin with median lobe broadly triangular, lateral margins slightly sinuous ( Fig. 2B View FIGURE 2 ).

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 View FIGURE 3 ); exopod slender, reaching proximal one-third of merus length, with flagellum ( Fig. 3A View FIGURE 3 ).

Adult chelipeds slightly asymmetrical ( Fig. 2A View FIGURE 2 ). Merus margins crenulate ( Fig. 2A View FIGURE 2 ). Carpus surface gently rugose, inner margin with sharp spine, with spinule basally ( Fig. 2A View FIGURE 2 ). 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 View FIGURE 3 ).

Ambulatory legs slender, surfaces and margins with scattered short setae ( Fig. 2A View FIGURE 2 ); second ambulatory leg longest, merus about 1.5 times as long as dactylus ( Fig. 2A View FIGURE 2 ).

Thoracic sternum surface generally smooth, weakly pitted ( Fig. 2C, D View FIGURE 2 ); sternites 1, 2 fused, forming triangular structure, separated from sternite 3 by conspicuous suture; sternites 3, 4 completely fused ( Fig. 2C, D View FIGURE 2 ). Male sternopleonal cavity reaching to imaginary line connecting median part of cheliped coxae ( Fig. 2C View FIGURE 2 ). Male pleonal locking tubercle on median part of sternite 5 ( Fig. 2D View FIGURE 2 ).

Male pleon triangular, surface smooth ( Fig. 2C View FIGURE 2 ); 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 View FIGURE 2 ). Female pleon ovate; somite 6 width about 2.5× length; telson semicircular, width about 2.0× length ( Fig. 4D View FIGURE 4 ).

G1 slender, straight ( Fig. 3B, C, G View FIGURE 3 ); tip exceeding pleonal locking tubercles in situ, reaching suture between thoracic sternites 4/5 ( Fig. 2D View FIGURE 2 ); 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 View FIGURE 3 , 5A View FIGURE 5 ), recurved in lateral view ( Fig. 5B View FIGURE 5 ); groove for G2 running mid-line of ventral surface ( Fig. 3B View FIGURE 3 ). G2 subterminal segment tapering distally, about 2.1× length of elongated terminal segment ( Fig. 3D View FIGURE 3 ). Vulvae on thoracic sternite 6, not reaching suture of sternites 5/6 anteriorly, elongate, ovate, closely spaced from one another, opening inwards ( Fig. 4E View FIGURE 4 ).

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 View FIGURE 6 ).

Habitat. This new species is characteristic of low-altitude hill streams, with sandy sediments under the stones ( Fig. 6B View FIGURE 6 ).

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 View FIGURE 3 , 5A View FIGURE 5 ), a distinctive character shared with nine congeners from nearby regions ( Fig. 7 View FIGURE 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 View FIGURE 3 , 5B View FIGURE 5 ), however, is a distinguishing character, and is a feature shared only with H. koatenense ( Fig. 5C View FIGURE 5 ; cf. Wang et al. 2022b: fig. 5B, C) and H. lini ( Fig. 5E View FIGURE 5 ; 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 View FIGURE 2 ) (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 View FIGURE 3 , 5B View FIGURE 5 ) (versus inner-distal angle relatively low, somewhat blunt in H. lini ; Fig. 5E, F View FIGURE 5 ; cf. Cheng et al. 2008: fig. 1(8)); G1 terminal segment with outer-distal angle more elongate ( Figs. 3B, G View FIGURE 3 , 5A View FIGURE 5 ) (versus terminal segment outer-distal angle relatively shorter in H. lini ; Fig. 5E, F View FIGURE 5 ; 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 View FIGURE 5 ) (versus outer-distal angle slightly recurved and relatively more slender in lateral view in H. lini ; Fig. 5F View FIGURE 5 ; 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 View 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 View FIGURE 4 ) (versus external orbital tooth broadly triangular in H. koatenense ; Fig. 4F–H View FIGURE 4 ), 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 View FIGURE 4 ) (versus epibranchial tooth relatively smaller, granular, separating from external orbital tooth by narrow V-shaped cleft in H. koatenense ; Fig. 4F–H View FIGURE 4 ). 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 View FIGURE 3 , 5A, B View FIGURE 5 ) (versus terminal segment with inner-distal angle relatively lower, globular in shape in H. koatenense ; Fig. 5C, D View FIGURE 5 ), and outer-distal angle strongly curved ventral-ward and relatively thin in lateral view ( Fig. 5B View FIGURE 5 ) (versus outer-distal angle almost straight and relatively thick in lateral view in H. koatenense ; Fig. 5D View FIGURE 5 ). Other subtle differences existing in the postorbital cristae, cleft between external orbital angle and epibranchial tooth are listed in Table 1 View TABLE 1 .