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

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Chasmocarcinus arcuatus Coelho & Coelho, 1998


Chasmocarcinus arcuatus Coelho & Coelho, 1998 

( Figs. 2View FIGURE 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.GoogleMaps 

Paratypes: 2 males ( MZUSPAbout MZUSP 13605View Materials, ex-DOUFPE 536; see Melo et al. 2003: 431), Brazil, Amapá, Almirante Saldanha , stn 7628, 01°19.5’N, 48°9.4'W, 31.05.1971GoogleMaps  ; 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) ( ZRCAbout ZRC 2015.220View Materials, ex MZUSPAbout MZUSP 32380View Materials), 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.GoogleMaps  —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. 2View FIGURE 2 E‒H; Coelho & Coelho 1998: fig. 1a–c). Front straight or slightly bilobed. Orbits short, proportionally short eye peduncles ( Fig. 21View FIGURE 21 B‒D; Coelho & Coelho 1998: fig. 1c, d). Epistome ( Fig. 21View FIGURE 21 B, C) with semicircular median lobe with median fissure, lateral margins straight. Antennular articles relatively short ( Fig. 21View FIGURE 21 C). Third maxilliped ( Fig. 28View FIGURE 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. 35View FIGURE 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. 35View FIGURE 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. 35View FIGURE 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. 2View FIGURE 2 G, H; Coelho & Coelho 1998: figs. 1a, 2c, 3c–e), inner surface setose. Inner margin of cheliped carpus smooth ( Fig. 2View FIGURE 2 G, H; Coelho & Coelho 1998: fig. 4b). Fused thoracic sternites 1, 2 ( Fig. 49View FIGURE 49 C, D; Coelho & Coelho 1998: fig. 4b) broadly triangular, proportionally narrow, short. Ambulatory legs ( Fig. 2View FIGURE 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. 49View FIGURE 49 C, D; 56B, C; Coelho & Coelho 1998: fig. 4c) with proportionally long, narrow telson. G1 ( Fig. 63View FIGURE 63 D, E, G‒I; Coelho & Coelho 1998: fig. 4d) medium size, slightly stout, spinules along distal half. G2 ( Fig. 63View FIGURE 63 F, J) about 3/4 G1 length, straight, slender, distal segment long, curved. Female pleon ( Fig. 84View FIGURE 84 B) with lateral margins of somites strongly convex; telson proportionally short. Sterno-pleonal cavity of female ( Fig. 89View FIGURE 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. 35View FIGURE 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).


Museu de Zoologia da Universidade de Sao Paulo


Zoological Reference Collection, National University of Singapore














Chasmocarcinus arcuatus Coelho & Coelho, 1998

Ng, Peter K. L. & Castro, Peter 2016


Chasmocarcinus peresi

Costa 1968: 335