Chasmocarcinus chacei Felder & Rabalais, 1986

Ng, Peter K. L. & Castro, Peter, 2016, Revision of the family Chasmocarcinidae Serène, 1964 (Crustacea, Brachyura, Goneplacoidea), Zootaxa 4209 (1), pp. 1-182 : 17-18

Chasmocarcinus chacei Felder & Rabalais, 1986

( Figs. 3 A, B; 21E; 28F; 35I, J; 49E; 56D; 63K–M; 84C; 89C)

Chasmocarcinus chacei Felder & Rabalais, 1986: 548 , figs. 1–3 [type localilty: Gulf of Mexico].— Blow & Bailey 1992: 176 [in list].—Felder et al. 2009: 1081 [in list].—Ng et al. 2008: 76 [in list].— Thoma et al. 2009: 558, 559 [Gulf of Mexico]. Chasmocarcinus cylindricus — Pequegnat 1970: 195.— Pequegnat et al. 1971: 3, pl. 2A [map].— Powers 1977: 12 (part).— Soto 1985: 487, table 1 (part).

Type material. Holotype female (6.6 × 7.5 mm) ( USNM 228455 ), northwestern Gulf of Mexico, East Flower Gardens Banks , NMFS Survey, stn PLB 8, 27°53.97’N, 93°34.79’W, 126 m, 21.10.1982.

Paratypes: 1 female ( USNM 228457 ), northwestern Gulf of Mexico, East Flower Gardens Banks , NMFS Survey, stn PLB 2, 27°53’41”N, 93°34’33”W, 128 m, 21.10.1982; 1 male (4.4 × 5.0 mm) (USNM 228458), 1 male exoskeleton (4.5 × 6.7 mm) (USNM 228456), 27°53.68’N 93°34.54’W, 128 m, 21.10.1982.

Other material examined. Gulf of Mexico. Holotype female (6.6 × 7.5 mm) ( USNM 228455 ), East Flower Gardens Banks , NMFS Survey, stn PLB 8, 27°53.97’N, 93°34.79’W, 126 m, 21.10.1982.—1 male (6.6 × 8.0 mm), 1 female (7.8 × 9.5 mm) (USNM 61489), White Shoals, Dry Tortugas, Florida, W.L. Schmitt coll., 75‒140 m, 27.07.1924.—1 male (USNM 74856), south of Dry Tortugas, Florida, W.L. Schmitt coll., 88 m, 28.07.1932.—1 male (4.8 × 6.7 mm), 1 female (5.4 × 6.0 mm) (ZRC 2013.1417), stn NGMx, 78°07.18’N, 90°56.812’W, 116‒117 m, mud, benthic skimmer, D. Felder & S. Tuederieas coll., 21.04.2011.

Diagnosis. Anterolateral margins of carapace ( Fig. 3 C‒E; Felder & Rabalais 1986: fig. 2a, b) smooth, without granular ridges. Orbits ( Fig. 21 F; Felder & Rabalais 1986: fig. 2a, b) short, proportionally long eye peduncles. Epistome ( Fig. 21 F; Felder & Rabalais 1986: fig. 2c) with semicircular median lobe with median fissure, lateral margins straight. Antennular articles relatively short ( Fig. 21 E). Third maxilliped ( Fig. 28 F) merus ovate; ischium rectangular, longer than merus. Bulging pterygostomial region, clearly visible from dorsal view. Fingers of major chela of both sexes ( Fig. 35 I; Felder & Rabalais 1986: fig. 3b) straight, proportionally short, only slightly longer than propodus in dorsal view; pollex as long as dactylus in large males. Fingers of minor chela of both sexes ( Fig. 35 J; Felder & Rabalais 1986: fig. 3c) scissor-like; cutting margin of pollex with low teeth, distal quarter with few small spines. Inner margin of cheliped carpus smooth. Ambulatory legs proportionally short ( Fig. 3 A, B: Felder & Rabalais 1986: fig. 3d), folded P5 merus only reaching middle portion of anterolateral margin; subdistal spur present on P5 dactylus ( Fig. 63 M). Fused thoracic sternites 1, 2 ( Fig. 49 E) broadly triangular, proportionally wide, short. Male pleon ( Felder & Rabalais 1986: fig. 2f) with proportionally long, narrow telson. G1 ( Fig. 63 K; Felder & Rabalais 1986: fig. 3f, g) stout, straight, distal segment with spinules. G2 ( Fig. 63 L; Felder & Rabalais 1986: fig. 3h) about 3/4 G1 length, straight, slender, distal segment long, curved. Female pleon ( Fig. 84 C) with lateral margins of somites strongly convex; telson proportionally short. Sterno-pleonal cavity of female ( Fig. 89 C) moderately shallow, vulvae close together.

Remarks. Diagnostic for C. chacei is a relatively smooth carapace that lacks granular ridges along the anterolateral margins, and proportionally short orbits and long eye peduncles ( Fig. 21 E; Felder & Rabalais 1986: fig. 2a, b), a rectangular third maxilliped ischium that is slightly longer than the merus ( Fig. 28 F), and semicircular, proportionally broad and short sternite 1 and 2 ( Fig. 49 E).

A molt of a large female from Anguilla (8.3 × 10.1 mm, USNM 228470), outside the normal distribution of C. chacei , and tentatively identified as belonging to this species ( Felder & Rabalais 1986: 549) actually represents C. typicus . The fused thoracic sternites 1 and 2 are broadly triangular with parallel sides, proportionally narrow and long, which is diagnostic for C. typicus .

Distribution. Gulf of Mexico. Depth: 86–296 m (Felder et al. 2009).

Figures

FIGURE 3. Overall dorsal view of species of Chasmocarcinus. A, C. chacei, Gulf of Mexico: male 6.6 × 8.0 mm (USNM 61489); B, C. chacei, Gulf of Mexico: female 7.8 × 9.5 mm (USNM 61489); C, C. cylindricus, Jamaica: male 3.6 × 4.9 mm (USNM 42942); D, C. cylindricus, Puerto Rico: neotype female 4.6 × 6.1 mm (USNM 23765); E, C. cylindricus, Puerto Rico: female 6.9 × 9.2 mm (USNM 24551); F, 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. 5 a).

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).