Nanhaipotamon longhaiense, Cai & Tan & Zou, 2021

Cai, Mao-Rong, Tan, Qi-Hong & Zou, Jie-Xin, 2021, A new species of freshwater crab of the genus Nanhaipotamon Bott, 1968 (Crustacea, Decapoda, Brachyura, Potamidae) from Longhai, Fujian Province, China, ZooKeys 1062, pp. 11-30 : 11

publication ID	https://dx.doi.org/10.3897/zookeys.1062.71171
publication LSID	lsid:zoobank.org:pub:AF8E0237-D372-4C23-97E3-F7898F471DA3
persistent identifier	https://treatment.plazi.org/id/E25133A7-AB4A-4CAA-8DF8-2DC9957384D9
taxon LSID	lsid:zoobank.org:act:E25133A7-AB4A-4CAA-8DF8-2DC9957384D9
treatment provided by	ZooKeys by Pensoft
scientific name	Nanhaipotamon longhaiense
status	sp. nov.

Treatment

Nanhaipotamon longhaiense sp. nov.

Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5A View Figure 5 , 6 View Figure 6 , 7 View Figure 7

Type material.

Holotype: ♂ (25.2 × 21.5 mm), China, Fujian Province, Longhai County, Chengxiang Town, Xiaye Village, 24°23'02"N, 117°34'76"E, alt. 55 m, 27 Aug. 2019, Mao-Rong Cai leg, NCU MCP 417701. Paratypes: 1 ♀ (allotype) (26.5 × 22.5 mm), same data as holotype, NCU MCP 428601; 2 ♂♂ (27.1 × 22.0 mm, 29.0 × 23.3 mm), same data as for holotype, ZZCDC 613201, ZZCDC 613203.

Other specimens examined.

9 ♂♂ (28.1 × 22.6 mm, 25.3 × 20.8 mm, 22.9 × 18.9 mm, 22.8 × 18.9 mm, 22.8 × 18.9 mm, 22.3 × 18.8 mm, 22.3 × 18.8 mm, 21.4 × 17.4 mm, 21.4 × 17.1 mm), same locality data as for holotype, 10 Aug. 2020, Mao-Rong Cai and Jie-Xin Zou leg, ZZCDC 613204 to 613208, TDRC 002101to 002104 ; 6 ♀♀ (26.4 × 22.2 mm, 23.4 × 18.9 mm, 21.6 × 17.7 mm, 21.2 × 16.8 mm, 21.2 × 16.2 mm, 18.4 × 15.2 mm), same locality data as for preceding, ZZCDC 613213 to 613215, TDRC 002105 to 002107 .

Diagnosis.

Carapace subquadrate, regions indistinct, anterolateral regions slightly rugose; cervical groove shallow and wide, H-shaped groove shallow; postorbital cristae sharp, almost fused with epigastric cristae (Figs 1A View Figure 1 , 3A View Figure 3 ). External orbital angle triangular, separated from anterolateral margin by wide, concave notch; epibranchial teeth small, granular; anterolateral margin lined with conspicuous granules (Figs 1A View Figure 1 , 3A View Figure 3 ). Third maxilliped merus with shallow median depression, exopod flagellum slightly longer than 1/3 exopod length (Fig. 2D View Figure 2 ). Chelipeds strongly unequal; fingers with small gap when closed (Figs 1A View Figure 1 , 3A View Figure 3 ). G1 slender, inner distal angle semicircular, inner margin of terminal segment convex, distal margin flat, outer distal angle blunt, laterally bent outwards at angle of about 60° (Figs 4A-D View Figure 4 , 5A View Figure 5 ). Female vulvae ovate, medium-sized, wholly within sternite 6, opening directed inward (Fig. 3B View Figure 3 ).

Description.

Carapace subquadrate, broader than long; dorsal surface smooth, distinctly convex longitudinally, with tiny pits; anterolateral region rugose. Branchial regions swollen (Figs 1A View Figure 1 , 3A View Figure 3 ). Cervical groove shallow and wide; H-shaped groove between gastric and cardiac regions shallow (Figs 1A View Figure 1 , 3A View Figure 3 ). Epigastric cristae conspicuous, separated by narrow gap; postorbital cristae sharp, almost fused with epigastric cristae (Figs 1A View Figure 1 , 3A View Figure 3 ). Front distinctly deflexed, margin ridged in dorsal view. External orbital angle triangular, separated from anterolateral margin by wide, concave notch. Epibranchial tooth small, granular. Anterolateral margin distinctly cristate, lined with approximately 20 granules (Figs 1A View Figure 1 , 3A View Figure 3 ). Posterolateral surface smooth, with inconspicuous oblique striae, converging towards posterior carapace margin (Figs 1A View Figure 1 , 3A View Figure 3 ). Orbits large; supraorbital, infraorbital margins cristate. Sub-orbital regions covered with granules (Fig. 1B View Figure 1 ); pterygostomial regions covered with large rounded granules; sub-hepatic regions covered with striae (Fig. 1B View Figure 1 ). Posterior margin of epistome with median triangle, lateral margin sinuous (Fig. 1B View Figure 1 ).

Third maxilliped merus about 1.2 times as broad as long, trapezoidal, with median depression; ischium about 1.3 times as long as broad, rectangular, with distinct median sulcus; exopod reaching approximately 1/4 of merus length, exopod flagellum slightly longer than 1/3 exopod length (Fig. 2D View Figure 2 ).

Chelipeds strongly unequal. Merus cross-section trigonal, inner-lower margin crenulated. Carpus surface weakly wrinkled, with longitudinal depression and sharp spine at inner-distal angle with spinule at base. Palm of larger chela about 1.3 times as long as high. Movable finger (dactylus) slightly shorter than the immovable finger (pollex). Inner margin of fingers with rounded, blunt teeth; fingers forming small gap when closed (Figs 1A View Figure 1 , 3A View Figure 3 ).

Ambulatory legs slender, second leg longest, merus 0.5-0.6 times as long as carapace length; last leg with propodus 2.1 times as long as broad, slightly shorter than dactylus. Dactylus gently curved, with sharp spines on the surface (Figs 2C View Figure 2 , 3A View Figure 3 ).

Male thoracic sternum smooth, pitted (Fig. 2A View Figure 2 ). Sternites 1, 2 completely fused to form triangular structure; sternites 2,3 separated by visible suture; sternites 3, 4 fused without obvious suture (Fig. 2A View Figure 2 ). Male sterno-pleonal cavity relatively deep, exceeding imaginary line connecting posterior edges of cheliped coxae (Fig. 2B View Figure 2 ). Median longitudinal suture of sternites 7, 8 deep and long. Tubercle of abdominal lock positioned at mid-length of sternite 5 (Fig. 2B View Figure 2 ). Female vulvae ovate, medium-sized, wholly within sternite 6, opening directed inward (Fig. 3B View Figure 3 ).

Male abdomen triangular; somites 4-6 gradually narrowed longitudinally, lateral margins slightly convex; somite 6 about 2.2 times as wide as long; telson about 1.4 times as wide as long (Fig. 2A View Figure 2 ).

G1 slender, tip of terminal segment reaches beyond pleonal locking tubercle (Fig. 2B View Figure 2 ), subterminal segment about 2.4 times as long as terminal segment (Fig. 4A View Figure 4 ). Inner distal angle semicircular, inner margin of terminal segment convex, distal margin flat, outer distal angle blunt, bent outwards at angle of about 60° (Figs 4A-D View Figure 4 , 5A View Figure 5 ). G2 subterminal segment about 1.9 times length of distal segment (Fig. 4E View Figure 4 ).

Etymology.

The new species is named after the county where is located, Longhai County, Zhangzhou City, Fujian Province, China.

Distribution.

Longhai County, Zhangzhou City, Fujian Province, China.

Ecology.

The new species occurs in the wetlands of low-elevation hills and mountains, amongst dense vegetation where there is little to no water flow year-round (Fig. 7B View Figure 7 ). During the day, the crabs usually hide in mud burrows close to the water source (Fig. 7A View Figure 7 ) or hide under rocks under water. We observed a berried female in August, suggesting the time around this month to be a part of the breeding season (Fig. 3C View Figure 3 ).

Remarks.

With a convex carapace dorsal surface, unequal chelipeds and triangular male abdomen, Nanhaipotamon longhaiense sp. nov. fits the diagnosis of Nanhaipotamon . Like some species within this genus, N. longhaiense sp. nov. shows intraspecific variation in G1 morphology, the distal margin of the G1 terminal segment is flat to oblique (Fig. 6A-C View Figure 6 ). In the holotype, the distal margin is flat (Fig. 6A View Figure 6 ), whereas in some adult specimens, the distal margin is oblique (Fig. 6B, C View Figure 6 ), and the inner margin of the G1 terminal segment is slightly convex to distinctly convex (Fig. 6A-C View Figure 6 ).

We make comparisons between the new species and seven species of Nanhaipotamon , among which N. wuping and N. macau are morphologically similar to this new species, N. yongchuense , N. huaanense and N. nanriense are geographically close ( Dai 1999), and N. guangdongense and N. hepingense are from Guangdong near Fujian ( Dai 1999). Nanhaipotamon longhaiense sp. nov. can be differentiated from its congeners by its unique G1 (Fig. 5A View Figure 5 ). Compared to N. longhaiense sp. nov., which has a semicircular G1 terminal segment inner distal angle, N. guangdongense , N. hepingense , N. yongchuense , N. nanriense , and N. huaanense differ in having instead a bluntly triangular G1 terminal segment inner distal angle (Fig. 5B-F View Figure 5 ). The G1 terminal segment inner distal angle is also semicircular in both N. wupingense and N. macau ( Huang et al. 2018a); however, the terminal segments in these two species are proportionately larger. In N. macau , the G1 terminal segment distal margin is sinuous to V-shaped (cf. Huang et al. 2018a: fig. 5D, E). In N. wupingense , the G1 terminal segment distal margin is sinuous to an inverte V-shaped (cf. Cheng et al. 2003: fig. 7; Huang et al. 2018a: fig. 6D). In N. longhaiense sp. nov., however, the G1 terminal segment distal margin is flat to oblique (Fig. 6A-C View Figure 6 ). The detailed differences between the new species and congeners are presented in Table 2 View Table 2 .