Chasmocarcinus arcuatus Coelho & Coelho, 1998

Ng, Peter K. L. & Castro, Peter, 2016, Revision of the family Chasmocarcinidae Serène, 1964 (Crustacea, Brachyura, Goneplacoidea), Zootaxa 4209 (1), pp. 1-182 : 17

Chasmocarcinus arcuatus Coelho & Coelho, 1998

( Figs. 2 E–H; 21B‒D; 28D, E; 35E‒H; 49C, D; 56B, C; 63D‒J; 84B; 89B)

Chasmocarcinus peresi Rodrigues da Costa, 1968: 335 [Brazil] (part).

Chasmocarcinus sp. D— Coelho et al. 1980: 39, 81, 86, table III, appendix II [in list].— Barreto et al. 1993: 651 [in list]. Chasmocarcinus arcuatus Coelho & Coelho, 1998: 800 , 805, 813, figs. 1‒4 [type localilty: Brazil].— Coelho et al. 2008: 12 [in list].—Ng et al. 2008: 76 [in list].

Type material (not examined). Holotype male (5.5 × 6.8 mm) (DOUFPE 534), Brazil, Amapá, Almirante Saldanha , stn 2497, 04°00’N, 50°34'W, 50 m, 31.05.1971.

Paratypes: 2 males ( MZUSP 13605 , ex-DOUFPE 536; see Melo et al. 2003: 431), Brazil, Amapá, Almirante Saldanha , stn 7628, 01°19.5’N, 48°9.4'W, 31.05.1971 ; 1 female (DOUFPE 528); 2 specimens of unknown sex (DOUFPE 529, DOUFPE 531, DOUFPE 535).

Material examined. Brazil. 1 male (3.7 × 5.1 mm), 1 ovigerous female (4.6 × 6.1 mm) ( ZRC 2015.220 , ex MZUSP 32380 ), stn 52/CB 90, 19°33’S, 39°34’W, TAAF MD 55/ Brésil 1987, Expédition Museúm Paris—USU/ Rio de Janeiro, 34 m, bottom with dead shells, 29.05.1987. —1 male (5.7 × 7.7 mm) (ZRC 2015.221, ex MZUSP 17485), PROMARLAN, macrofauna 11C, 08.2004; 1 female (4.4 × 6.2 mm) (ZRC 2015.222, ex MZUSP 17486), PROMARLAN, stn CAB3A, 0 8.2004.

Diagnosis. Anterolateral margins of carapace with conspicuous granular ridge ( Fig. 2 E‒H; Coelho & Coelho 1998: fig. 1a–c). Front straight or slightly bilobed. Orbits short, proportionally short eye peduncles ( Fig. 21 B‒D; Coelho & Coelho 1998: fig. 1c, d). Epistome ( Fig. 21 B, C) with semicircular median lobe with median fissure, lateral margins straight. Antennular articles relatively short ( Fig. 21 C). Third maxilliped ( Fig. 28 D, E; Coelho & Coelho 1998: fig. 2a) ischium rectangular, slightly longer than ovate merus. Bulging pterygostomial region, clearly visible from dorsal view. Fingers of major chela of large males ( Fig. 35 E; Coelho & Coelho 1998: figs. 1a, 2c, 3d, e) with curved, arched fingers, wide gap, proportionally short, slightly shorter than propodus in dorsal view; pollex as long as dactylus, 2 large, conspicuous teeth on pollex. Fingers of major chelae of females, small males ( Fig. 35 G; Coelho & Coelho 1998: fig. 2e, 3a–c) straight, about as long as propodus, narrow gap without 2 conspicuous teeth on pollex. Fingers of minor chela of both sexes ( Fig. 35 F, H; Coelho & Coelho 1998: fig. 2d, f) subcircular in cross-section, scissor-like; with small, often sharp teeth. Outer surface of carpus of major chela of large males eroded ( Fig. 2 G, H; Coelho & Coelho 1998: figs. 1a, 2c, 3c–e), inner surface setose. Inner margin of cheliped carpus smooth ( Fig. 2 G, H; Coelho & Coelho 1998: fig. 4b). Fused thoracic sternites 1, 2 ( Fig. 49 C, D; Coelho & Coelho 1998: fig. 4b) broadly triangular, proportionally narrow, short. Ambulatory legs ( Fig. 2 E, G, H) proportionally short, folded P5 merus only reaching middle portion of anterolateral margin; no subdistal spur on P5 dactylus. Male pleon ( Figs. 49 C, D; 56B, C; Coelho & Coelho 1998: fig. 4c) with proportionally long, narrow telson. G1 ( Fig. 63 D, E, G‒I; Coelho & Coelho 1998: fig. 4d) medium size, slightly stout, spinules along distal half. G2 ( Fig. 63 F, J) about 3/4 G1 length, straight, slender, distal segment long, curved. Female pleon ( Fig. 84 B) with lateral margins of somites strongly convex; telson proportionally short. Sterno-pleonal cavity of female ( Fig. 89 B) moderately shallow, vulvae close together.

Remarks. Diagnostic only of the major chela of large males of C. arcuatus are the arched cheliped fingers ( Fig. 35 E; Coelho & Coelho 1998: figs. 1a, 2c, 3d, e), the wide gape of the fingers, pollex armed with two teeth, and the eroded outer surface of the propodus. These characters could not be verified in the material examined and are based only on the description of Coelho & Coelho (1998). The granular ridge along the anterolateral margins of the carapace tends to be more elevated than that of its Brazilian congeners. Chasmocarcinus arcuatus is contrasted with C. meloi Coelho & Coelho, 1998 , in the discussion of the latter taxon.

Distribution. Brazil (Amapá to Espírito Santo). Depth: 21‒75 m (Coelho & Coelho 1998).

Figures

FIGURE 2. Overall dorsal view of species of Chasmocarcinus. A, C. typicus, Trinidad: holotype male 7.8 × 8.7 mm (USNM 6901); B, C. typicus, Trinidad: paratype male 4.1 × 4.7 mm (USNM 6901); C, C. typicus, Brazil: male 4.0 × 5.1 mm (MCZ CRU- 10993, holotype of C. rathbuni); D, C. typicus, Brazil: female 8.6 × 10.5 mm (ZRC 2015.211); E, C. arcuatus, Brazil: male 5.7 × 7.7 mm (ZRC 2015.221); F, C. arcuatus, Brazil: female 4.4 × 6.2 mm (ZRC 2015.222); G, C. arcuatus, Brazil: male 3.7 × 5.1 mm (ZRC 2015.220); H, C. arcuatus, Brazil: ovigerous female 4.6 × 6.1 mm (ZRC 2015.220).

FIGURE 21. Frontal view of cephalothorax of species of Chasmocarcinus. A, C. typicus, Trinidad: holotype male 7.8 × 8.7 mm (USNM 6901); B C. arcuatus, Brazil: male 5.7 × 7.7 mm (ZRC 2015.221); C, D, C. arcuatus, Brazil: male 3.7 × 5.1 mm (ZRC 2015.220); E, C. chacei, Gulf of Mexico: male 6.6 × 8.0 mm (USNM 61489); F, C. cylindricus, Puerto Rico: neotype female 4.6 × 6.1 mm (USNM 23765); G, C. gemmatus n. sp., Costa Rica: male 7.7 × 11.6 mm (SIO C 1205); H, C. hirsutipes, Brazil: holotype female 6.6 × 7.0 mm (after Coelho & Coelho 1998: fig. 5 c).

FIGURE 28. Third maxilliped of species of Chasmocarcinus and Amboplax n. gen. A, Chasmocarcinus typicus, Trinidad: holotype male 7.8 × 8.7 mm (USNM 6901); B, Chasmocarcinus typicus, Brazil: male 4.0 × 5.1 mm (MCZ CRU- 10993, holotype of Chasmocarcinus rathbuni); C, Chasmocarcinus typicus, Brazil: male 9.4 × 12.1 mm (ZRC 2015.211); D, Chasmocarcinus arcuatus, Brazil: male 5.7 × 7.7 mm (ZRC 2015.221); E, Chasmocarcinus arcuatus, Brazil: male 3.7 × 5.1 mm (ZRC 2015.220); F, Chasmocarcinus chacei, Gulf of Mexico: female 7.8 × 9.5 mm (USNM 61489); G, Chasmocarcinus cylindricus, Puerto Rico: female 6.9 × 9.2 mm (USNM 24551); H, Amboplax peresi, Brazil: male 5.1 × 6.4 mm (ZRC 2015.217).

FIGURE 35. Chelae of species of Chasmocarcinus. A, C. typicus, Trinidad: holotype male 7.8 × 8.7 mm (USNM 6901); B, C. typicus, Brazil: male 4.0 × 5.1 mm (MCZ CRU- 10993, holotype of Chasmocarcinus rathbuni); C, D, C. typicus, Trinidad: paratype male 7.1 × 9.4 mm (USNM 6901); E, F, C. arcuatus, Brazil: holotype male 5.5 × 6.8 mm (after Coelho & Coelho 1998: figs. 2 d, 3 e); G, H, C. arcuatus, Brazil: male 3.7 × 5.1 mm (ZRC 2015.220); I, J, C. chacei, Gulf of Mexico: male 6.6 × 8.0 mm (USNM 61489); K, L, C. cylindricus, Jamaica: male 3.6 × 4.9 mm (USNM 42942).

FIGURE 49. Anterior thoracic sternum and male pleon of species of Chasmocarcinus. A, C. typicus, Trinidad: holotype male 7.8 × 8.7 mm (USNM 6901); B, C. typicus, Brazil: male 4.0 × 5.1 mm (MCZ CRU- 10993, holotype of Chasmocarcinus rathbuni); C, C. arcuatus, Brazil: male 5.7 × 7.7 mm (ZRC 2015.221); D, C. arcuatus, Brazil: male 3.7 × 5.1 mm (ZRC 2015.220); E, C. chacei, Gulf of Mexico: male 6.6 × 8.0 mm (USNM 61489); F, C. cylindricus, Jamaica: male 3.6 × 4.9 mm (USNM 42942); G, C. gemmatus n. sp., Costa Rica: male 7.7 × 11.6 mm (SIO C 1205); H, C. hirsutipes, Brazil: holotype male 6.6 × 7.0 mm (after Coelho & Coelho 1998: fig. 7 c).

FIGURE 63. Gonopods and ambulatory dactylus of species of Chasmocarcinus. A ‒ C, C. typicus, Trinidad: holotype male 7.8 × 8.7 mm (USNM 6901); D ‒ F, C. arcuatus, Brazil: male 5.7 × 7.7 mm (ZRC 2015.221); G ‒ J, C. arcuatus, Brazil: male 3.7 × 5.1 mm (ZRC 2015.220); K ‒ M, C. chacei, Gulf of Mexico: paratype male 4.5 × 6.7 mm (USNM 228456, after Felder & Rabalais 1986: fig. 3 e, g, h). A, D, G, ventral view of left G 1; B, E, H, dorsal view of left G 1; I, ventral view of tip of left G 1; K, ventral view of right G 1 (laterally transposed); C, F, J, L, left G 2; M, tip of P 5. Scales: A ‒ H, J ‒ M = 0.5 mm; I = 0.1 mm.

FIGURE 84. Female thoracic sternum and pleon of species of Chasmocarcinus. A, C. typicus, Trinidad: paratype female 6.5 × 6.8 mm (USNM 6901); B, C. arcuatus, Brazil: female 4.4 × 6.2 mm (ZRC 2015.222); C, C. chacei, Gulf of Mexico: female 7.8 × 9.5 mm (USNM 61489); D, C. cylindricus, Puerto Rico: female 6.9 × 9.2 mm (USNM 24551); E, C. latipes, Mexico: neotype female 12.4 × 14.4 mm (USNM 21592); F, C. latipes, Mexico: female 9.2 × 13.0 mm (AMNH 16262, holotype female of Chasmocarcinus ferrugineus Glassell, 1936).

FIGURE 89. Vulvae of species of Chasmocarcinus, Amboplax n. gen. and Deltopelta n. gen. A, Chasmocarcinus typicus, Trinidad: paratype female 6.5 × 6.8 mm (USNM 6901); B, Chasmocarcinus arcuatus, Brazil: female 4.4 × 6.2 mm (ZRC 2015.222); C, Chasmocarcinus chacei, Gulf of Mexico: female 7.8 × 9.5 mm (USNM 61489); D, Chasmocarcinus cylindricus, Puerto Rico: female 6.9 × 9.2 mm (USNM 24551); E, Chasmocarcinus latipes, Mexico: holotype female 12.4 × 14.4 mm (USNM 21592); F, C. latipes, Mexico: female 9.2 × 13.0 mm (AMNH 16262, holotype female of Chasmocarcinus ferrugineus Glassell, 1936); G, Chasmocarcinus longipes, Colombia: paratype female 5.6 × 6.8 mm (USNM 78785); H, Chasmocarcinus mississippiensis, Gulf of Mexico: female 9.6 × 12.4 mm (USNM 150090); I, Amboplax peresi, Brazil: ovigerous female 4.9 × 6.2 mm (ZRC 2015. 217); J, Deltopelta obliquus, Belize: female 10.7 × 13.0 mm (PMNH, holotype of Hephthopelta superba).