Capitamon capitatum, Pati & Peter & L., 2024

Pati, Sameer K., Mitra, Santanu & Ng, Peter K. L., 2024, Identity of the freshwater crab Indochinamon beieri (Pretzmann, 1966), with the description of a new genus and four new species from northeastern India (Decapoda, Brachyura, Potamidae), Zoosystema 46 (23), pp. 589-615 : 598-602

Capitamon capitatum n. sp.

( Figs 5 ; 6 ; 7 )

urn:lsid:zoobank.org:act:66331159-75CC-4D8E-B15A-B65CCD51A361

TYPE MATERIAL. — Holotype. India • ♂ (49.5 × 37.3 mm); Nagaland: Tuensang district: Konya ; 26°15’36”N, 94°51’35”E; alt. 1660 m; 20.VII.2017; Khampong leg.; ZSI-WRC C.2400 .

Paratypes. India • 2 ♂ (47.7 × 36.1 mm, 47.3 × 35.7 mm), 2 ♀ (49.6 × 38.4 mm, 45.1 × 34.9 mm); same data as for holotype; ZSI-WRC C.2401 .

OTHER MATERIAL. — India • ♂, 2 ♀; Arunachal Pradesh: Anjaw district: Manchila ; 28°5’20”N, 96°27’32”E; alt. 931 m; 22.XI.2022; S. D. Gurumayum leg.; ZSI-WRC C.2402 • ♂, ♀; Arunachal Pradesh: Anjaw district: Khupa, Hayuliang ; 28°4’26”N, 96°28’58”E; alt. 690 m; 23.XI.2022; S. D. Gurumayum leg.; ZSI-WRC C.2403 • 5 ♂, 5 ♀; Arunachal Pradesh: Anjaw district: Knyao Stream, Hayuliang ; 28°4’15”N, 96°34’8”E; alt. 677 m; 24.XI.2022; S. D. Gurumayum leg.; ZSI-WRC C.2404 .

DIAGNOSIS. — Carapace ovate, broader than long (CW/CL = 1.4), relatively low ( CH /CW = 0.4); epigastric cristae well-developed, rugose; postorbital cristae well-developed, relatively sharp, straight in dorsal view; external orbital angle triangular, with short outer margin, c. 2 × inner margin; epibranchial tooth low, blunt, positioned above level of postorbital cristae; cervical grooves continuous, reaching to level of postorbital cristae; epistome posterior margin with well-developed, triangular median tooth, outer parts sloping downwards laterally ( Fig. 5A, B ). Third maxilliped exopod lacking flagellum or with vestigial flagellum ( Fig. 6B ). Chelipeds rugose, unequal, inner distal tooth on carpus relatively broad ( Figs 5A, C ; 6C ). Male s3/s4 shallow, running from sternopleonal cavity to lateral edges of sternum ( Figs 5C ; 6D ). Male pleonal somite 6 relatively broader (proximal width c. 2.0 × medial length), equal in length to pleonal somite 5, with almost straight lateral margins ( Figs 5C ; 6E ). Male telson relatively broader (proximal width c. 1.3 × medial length), with strongly concave lateral margins ( Figs 5C ; 6E ). G1 ultimate article relatively less strongly bent at angle of about 75° from longitudinal axis, with sinuous outer margin, dorsal flap relatively low, broadly triangular ( Figs 6F ; 7A , C-E). G2 c. 1.1 × length of G1; ultimate article long, c. 0.5 × length of penultimate article ( Figs 6F, G ; 7B, D ). Vulvae laterally completely covered by protruding sternal cover, invisible in ventral view ( Fig. 6I ).

ETYMOLOGY. — The specific epithet is an adjective in the Latin nominative singular meaning having a head, referring the head-like ultimate article of the male first gonopod of the type species.

GEOGRAPHICAL DISTRIBUTION. — Capitamon capitatum n. gen., n. sp. is known only from Arunachal Pradesh and Nagaland states of northeastern India ( Fig. 1 ).

REMARKS

Capitamon capitatum n. gen., n. sp. is unique among the nominal species of the genus because of the straight postorbital cristae in dorsal view ( Fig. 5A ) (vs postorbital cristae oblique in dorsal view; Figs 8A ; 9A ; 12A ; 15A ; see Pati et al. 2020: figs 1a; 2a) and the vestigial or missing flagellum on the third maxilliped exopod ( Fig. 6B ) (vs flagellum on the third maxilliped exopod relatively longer, equal to or more than half the width of the merus; Figs 9B ; 13B ; 16B ; see Pati et al. 2020: fig. 2c).

The G1 ultimate article of C. capitatum n. gen., n. sp. is similar in structure to that of C. clarki n. gen., n. sp. in that it is bent at an angle of about 75° from longitudinal axis of the G1, with the dorsal flap being relatively low and broadly triangular ( Figs 6F ; 7A , C-E; 8C; 10A, B, D). The outer margin of the G1 ultimate article, however, is sinuous in C. capitatum n. gen., n. sp. ( Figs 6F ; 7A , C-E), whereas the outer margin of the said structure is straight in C. clarki n. gen., n. sp. ( Figs 8C ; 10A, B, D ). The following differences between them can also be noted: the carapace is relatively low ( CH /CW = 0.4) in C.capitatum n. gen., n. sp. ( Fig. 5B ) against the relatively high carapace ( CH /CW = 0.5) in C. clarki n. gen., n. sp. ( Fig. 9C ); the male pleonal somite 6 is equal in length to the pleonal somite 5 in C. capitatum n. gen., n. sp. ( Figs 5C ; 6E ) against the longer male pleonal somite 6 than the pleonal somite 5 in C. clarki n. gen., n. sp. ( Figs 8B ; 9D ); and the lateral margins of the male telson is strongly concave in C. capitatum n. gen., n. sp. ( Figs 5C ; 6E ) against the gently concave lateral margins of the male telson in C. clarki n. gen., n. sp. ( Figs 8B ; 9D ).

Figures

FIG. 5. — Capitamon capitatum n. gen., n. sp., holotype ♂ (49.5 × 37.3 mm) (ZSI-WRC C.2400): A, overall dorsal view; B, frontal view of cephalothorax; C, overall ventral view. Scale bars: A, C, 20 mm; B, 10 mm.

FIG. 6. — Capitamon capitatum n. gen., n. sp., holotype ♂ (49.5 × 37.3 mm) (ZSI-WRC C.2400) (A-G), paratype ♀ (49.6 × 38.4 mm) (ZSI-WRC C.2401) (H, I): A, mouthparts; B, right third maxilliped; C, chela (outer view); D, s1-s8 showing right G1 in situ; E, pleon and telson;F, left G1 (dorsal view); G, left G2; H, pleonal somites 3-6 and telson; I, s1-s8 showing vulvae. Scale bars: A, B, D, E, H, I, 5 mm; C, 10 mm; F, G, 2 mm.

FIG. 7. — Capitamon capitatum n. gen., n. sp., holotype ♂ (49.5 × 37.3 mm) (ZSI-WRC C.2400): A, left G1 ultimate article (dorsal view); B, left G2; C, left G1 ultimate article (ventral view); D, left G1 (dorsal view); E, left G1 (ventral view). Scale bar: A, C, 1 mm; B, D, E, 2 mm.

FIG. 1. — Map showing Myanmar, India, northeastern India, and distribution of Indochinamon beieri (Pretzmann, 1966) and the species of Capitamon n. gen.

FIG. 8. — Capitamon clarki n. gen., n. sp., holotype ♂ (42.1 × 32.9 mm) (NHM 1909.5.1.1): A, overall dorsal view; B, s1-s7, pleonal somites 4-6, and telson; C, left G1 (ventral view); D, left G2; E, s1-s8 showing right G1 in situ. Not to scale.

FIG. 9. — Capitamon clarki n. gen., n. sp., holotype ♂ (42.1 × 32.9 mm) (NHM 1909.5.1.1): A, dorsal view of cephalothorax; B, right third maxilliped; C, frontal view of cephalothorax; D, pleon and telson; E, chela (outer view). Not to scale.

FIG. 12. — Capitamon meitei n. gen., n. sp., holotype ♂ (51.7 × 38.8 mm) (ZSI-WRC C.2405): A, overall dorsal view; B, frontal view of cephalothorax; C, overall ventral view. Scale bars: A, C, 20 mm; B, 10 mm.

FIG. 15. — Capitamon mizoramense n. gen., n. sp., holotype ♂ (46.3 × 35.7 mm) (ZSIK C.6122/2A): A, overall dorsal view; B, frontal view of cephalothorax; C, overall ventral view. Scale bars: A, C, 20 mm; B, 10 mm.

FIG. 13. — Capitamon meitei n. gen., n. sp., holotype ♂ (51.7 × 38.8 mm) (ZSI-WRC C.2405) (A-G), paratype ♀ (36.0 × 27.4 mm) (ZSI-WRC C.2406) (H, I): A, mouthparts; B, right third maxilliped; C, chela (outer view); D, s1-s8 showing right G1 in situ; E, pleon and telson; F, left G1 (dorsal view); G, left G2; H, pleonal somites 3-6 and telson; I, s1-s8 showing vulvae. Scale bars: A, B, D, E, H, I, 5 mm; C, 10 mm; F, G, 2 mm.

FIG. 16. — Capitamon mizoramense n. gen., n. sp., holotype ♂ (46.3 × 35.7 mm) (ZSIK C.6122/2A) (A-G), paratype ♀ (51.3 × 37.6 mm) (ZSIK C.6122/2B) (H, I): A, mouthparts; B, right third maxilliped; C, chela (outer view); D, s1-s8 showing right G1 in situ; E, pleon and telson; F, left G1 (dorsal view); G, left G2; H, pleonal somites 3-6 and telson; I, s1-s8 showing vulvae. Scale bars: A, B, D, E, H, I, 5 mm; C, 10 mm; F, G, 2 mm.

FIG. 10. — Capitamon clarki n. gen., n. sp., holotype ♂ (42.1 × 32.9 mm) (NHM 1909.5.1.1): A, left G1 (ventral view);B, left G1 ultimate article (ventral view); C, left G2; D, left G1 ultimate article (dorsal view). Scale bar: A, C, 1 mm; B, D, 0.5 mm.