Arcotheres guinotae, Campos, 2001

Campos, Ernesto, 2001, A new crab species of the genus Arcotheres Manning, 1993, from Thailand (Crustacea, Brachyura, Pinnotheridae), Zoosystema 23 (3), pp. 493-497 : 494-497

Arcotheres guinotae n. sp.

( Figs 1 ; 2 )

TYPE MATERIAL. — 1, Thailand, cw 6.4 mm, cl 5.8mm, in the bivalve Barbatia sp. Raoul Serène coll. ( MNHN-B 9498).

TYPE LOCALITY. — Thailand.

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ETYMOLOGY. — This species is named in honor of Madame Danièle Guinot, MNHN, for her contributions to brachyuran systematics and support of my pinnotherid studies.

DESCRIPTION

Carapace subhexagonal, regions moderately defined, sharp anterolateral margins produced distally; front little produced, slightly emarginate, posterior margin slightly curved. Eyes pigmented, not visible dorsally, oval orbits with irregular margin. Antennules folded obliquely; antennular cavities little larger than orbits. Antennae of six segments, basal segment wide, with a prominent tubercle, distal segment setose, scarcely overreaching dorsal margin of oculo-antennular cavities. Epistome and labium separated, margin of first sternite emarginated.

Mxp3 obliquely placed in buccal cavity, ischium and merus indistinguishably fused, dorsal margin wide, curved, with short setae; ventral margin forms an angle, with long, slender setae. Palp of three segments, carpus subtrapezoidal, dorso-lateral margin curved, spatulate propodus longer than carpus, obliquely sub-truncated, both segments with a dorsal fringe of setae; digitiform dactylus distally setose, inserted medially in a notch on ventral margin of propodus, distally not overreaching tip of propodus and angle of ventral angle of merus. Exopod with a 3-segmented flagellum, minute distal segment inconspicuously articulated.

Chelipeds stouter than wl, merus slightly longer than trapezoidal carpus, chela globose, dorsal and ventral margin gently convex, outer surface of palm slightly convex, inner surface very convex; pollex conical, cutting edge proximally with two broadly, triangular teeth, separated by a denticulate notch in which subtruncated tooth of curved dactylus fits; both fingers with a distal row of spiniform tubercles and setae.

Wl asymmetrical in length; those of left side longer; wl1-2 similar in shape, wl2 longer, margins from merus to propodus without setae, propodi longer than carpi, curved lengthwise, conical dactylus fits about three times in its respective propodus, curved at tip, margins with scattered setae; wl3 markedly asymmetrical, with scattered setae on margins, shorter leg almost similar in shape and relative length to those segments of wl1-2, longer leg relatively slender, carpus and propodus more curved, sword-shaped dactylus, which is as long as propodus, ends in a small, curved tip; wl4 more slender than those of wl1-3, segments similar to those of wl3, but dactylus proportionally longer, curved; dactylus of wl4 with more setae on margins, those of ventral margin longer than those of dorsal margin. Relative length of wl 3>2>1>4.

Abdomen extremely wide, with six somites and telson well-separated, margin with tomentum, length and width of abdominal somites increasing from somite 1 to 5, then diminishing towards telson.

REMARKS

Arcotheres guinotae n. sp., A. similis ( Bürger, 1895) , A. spinidactylus ( Gordon, 1936) n. comb., A. tivelae ( Gordon, 1936) n. comb., and A. alcocki (Rathbun, 1910) n. comb. constitute a subgroup of species within the genus Arcotheres that can be recognized by the dactylus of mxp3 not reaching the tip of its propodus and the dactylus of wl4 being longer than that of wl3. Arcotheres guinotae n. sp. differs from A. similis and A. spinidactylus because setae on the ventral margin of the dactylus of wl4 are longer than those of its dorsal margin, instead of short and subequal setae on the dorsal and ventral margin of the dactylus of wl4 which is observed in the later two species; and from A. tivelae and A alcocki due the dactylus of wl 4 in these species being shorter than its respective propodus instead of dactylus longer than propodus as observed in A. guinotae n. sp. In addition, the acute and sinuous anterolateral margin of the carapace in A. guinotae n. sp., is not observed in all other known congeners.

Figures

FIG. 1. — Arcotheres guinotae n. sp., holotype, cw 6.4 mm, cl 5.8 mm; A, dorsal view; B, D, 1-4, inner view of left and right propodi and dactyli of wl respectively; C, abdomen. Scale bar: A, 1.74 mm; B, D, 1.16 mm; C, 1.52 mm.

FIG. 2. — Arcotheres guinotae n. sp., holotype, cw 6.4 mm, cl 5.8 mm; A, cheliped, inner view; B, frontal view; C, D outer and inner view of mxp3. Arrow indicates the antennal tubercle. Scale bar: A, 0.67 mm; B, 0.45 mm; C, D, 0.326 mm.