Pseudopalicus bidens, Promdam, Rueangrit & Nabhitabhata, Jaruwat, 2012

Promdam, Rueangrit & Nabhitabhata, Jaruwat, 2012, A new species of palicid crab (Crustacea, Decapoda: Brachyura: Palicidae) from the Andaman Sea, west coast of Thailand, Zootaxa 3513, pp. 79-85 : 80-84

publication ID	https://doi.org/ 10.5281/zenodo.282566
DOI	https://doi.org/10.5281/zenodo.5698341
persistent identifier	https://treatment.plazi.org/id/03C68790-6D5A-FFA9-FF4D-896BFE32F948
treatment provided by	Plazi
scientific name	Pseudopalicus bidens
status	sp. nov.

Treatment

Pseudopalicus bidens View in CoL new species

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

HOLOTYPE.—Male (8.1× 10.4 mm), BIOSHELF St. C5, western coast of Thailand, Andaman Sea (9°00'N, 97°25'E), Agassiz trawl, 215–230 m, coll. C. Aungtonya & V. Vongpanich, 0 2.02.2000 ( PMBC 26820).

PARATYPES.— 1 male (7.8×10.0 mm), BIOSHELF st. L6, west coast of Thailand, Andaman Sea (6°45'N, 98°06'E), Agassiz trawl, 303–313 m, coll. C. Aungtonya & V. Vongpanich, 23.02.2000 ( PMBC 26821).— 1 male (6.2× 7.9 mm), BIOSHELF st. I6, west coast of Thailand, Andaman Sea (7°30'N, 97°50'E), rectangular dredge, 299–301 m, coll. C. Aungtonya & V. Vongpanich, 9.11.1999 ( PMBC 26819).

TYPE LOCALITY.— BIOSHELF st. L6, Andaman Sea coast of Thailand, (6°45'N, 98°06'E), 303– 313 m.

ETYMOLOGY.—The name ‘ bidens ’ (Latin for “two-toothed) refers to the appearance of the anterolateral borders of the carapace, which seems to be armed with only two teeth on each side because of the first two teeth are much larger than the last two.

DISTRIBUTION.—Known only from the type locality on the Andaman Sea coast of Thailand.

DIAGNOSIS.—Carapace ( Figs. 2 View FIGURE 2 A–B, 4A) with 4 anterolateral teeth on each side, the first 2 teeth are broad, slightly pointed, first larger than second, much larger than the last 2 teeth. Dorsal surface of carapace with large granular bosses, 12 of which form an almost straight row across branchial, metagastric regions; posterior border with 6 low, elongated tubercles. Supraorbital borders each with 2 slightly rounded to triangular lobes; inner border slightly higher than outer. Outer surfaces of cheliped propodi ( Fig. 2 View FIGURE 2 D) with scattered thin, rounded tubercles of various sizes. Dactyli of walking legs (P2–4) slender, with posterior borders entire. Abdomen of mature males ( Fig. 3 View FIGURE 3 C) with all segments free, one complete transverse ridge along each segment 1-3, incomplete ridge along median portion of segment 4. G1 ( Figs. 3 View FIGURE 3 D–F, 4B–D) with sinuous basal parts with thick, mammillate tooth near extremity of ventral surface; each distal portion with spinules along outer margin, 2 slender, 3 small teeth on inner side, one thick, mammillate ventral tooth.

DESCRIPTION.—Carapace ( Figs. 2 View FIGURE 2 A–B, 4A) transversely hexagonal, wider than long (CW/CL = 1.3). Anterolateral borders of carapace each with 4 anterolateral teeth on each side, first 2 teeth broad, slightly pointed, the first larger than second, much larger than last two. Dorsal surface of carapace with large granular bosses, 12 of which form an almost straight row across the branchial, metagastric regions; posterior border with 6 low, elongated tubercles.

Frontal border of carapace divided into 4 narrow lobes, inner lobes longer, typically more pointed (outer teeth always shorter but may be pointed in some specimens). Borders between frontal lobes, supraorbital borders folded upward, rounded or slightly pointed medially, ending in sharp angle, forming V-shaped fissure before supraorbital border. Supraorbital borders each with 2 slightly rounded to triangular lobes; inner border being slightly higher than outer. Postorbital angles moderately long (extending almost to dorsal border of retracted eye), slender, slightly pointed inward. Cornea of the eyes dorsoventrally flattened, wider than base of short eye peduncle; each peduncle with three granular tubercles on distal border (median tubercles most conspicuous).

Suborbital borders ( Fig. 3 View FIGURE 3 A) each with one broad, square outer lobe; one higher, narrower, rounder inner lobe. Pterygostomial lobes project ventrally, forming a flat, semicircular structure posterior to each inner suborbital lobe.

Each basal antennal segment slender, rectangular (with slightly pointed distal border in ventral view); flagellum long, with few, simple setae. Epistome vertically inclined ( Figs. 2 View FIGURE 2 C, 3B), with 2 triangular, pointed median teeth, each flanked by triangular outer process, thin, rounded margin before pterygostomial lobe. Inner border of ischia of third maxillipeds ( Figs. 2 View FIGURE 2 C, 3A) straight; surface coarsely granular, with upper borders rounded. Meri ( Fig. 2 View FIGURE 2 C) much narrower than ischia; upper lobes straight with rounded outer borders.

Outer surfaces of cheliped propodi ( Fig. 2 View FIGURE 2 D) each with 4 thin processes, at least one of which expanded as high, thin, semicircular process. Fingers of male largest cheliped with cutting edges, 6 rounded to triangular teeth in smallest cheliped. Carpi short, outer borders with one thin, broadly rounded or triangular tubercle, several low, rounded tubercles; meri slender, distal portions of outer borders with rounded or pointed tubercles.

First 3 pairs of walking legs (P2–4; Fig. 2 View FIGURE 2 A) flattened. Upper, lower borders of meri with tubercles of different sizes and shapes (mostly pointed, some rounded; smaller but on 2 anterior rows in P2–3); distalmost tubercle on each anterior border much wider at the base, much higher, slender, pointed or rounded, directed distally. Anterior border of carpi of walking legs (P2–4) each with 2 large, triangular tubercles; borders of propodi entire. Each P2 with one row of tubercles on dorsal, 2 rows on ventral surface of merus; 2 dorsal, 2 ventral carinae each on carpus, propodus; one dorsal, one ventral carina on dactylus. Each P3 with one dorsal, 2 very low ventral rows of tubercles on merus; 2 dorsal, 2 ventral carinae each on carpus, propodus, dactylus. Each P4 with 2 dorsal, one very low ventral row of tubercles on merus; 2 dorsal, 2 ventral carinae on each carpus, propodus; one dorsal, 3 ventral carinae on dactylus. Meri of all walking legs with scattered plumose setae; dorsal surfaces of propodi, dactyli of P3–4, each with one row of conspicuous plumose setae along anterior border.

First pair of walking legs (P2) shorter, more slender than second, third pairs (P3–4); third pair slightly shorter than second. Fifth pair of pereopods (P5) short (0.9–1.0 CL); each merus slender, surface with microscopic tubercles, plumose setae along the posterior border; each propodus with 4 spines along posterior border; each dactylus with 4-6 spines along posterior border, 1–4 spines along anterior border, one terminal pointed tooth.

Abdomen of mature males ( Fig. 3 View FIGURE 3 C) with all segments free, one complete transverse ridge along each segment 1–3, incomplete ridge along median portion of segment 4. G1 ( Figs. 3 View FIGURE 3 D–F, 4B–D) with a sinuous basal parts with thick, mammillate tooth near extremity of ventral surface; each distal portion with spinules along outer margin with 2 slender and 3 small teeth on inner side, one thick, mammillate ventral tooth.

Females unknown.

REMARKS.— Pseudopalicus bidens new species shares some characteristics with P. declivis Castro, 2000 and P. sexlobatus (Kensley 1969) by having walking legs (P2–4) dactyli that are long, slender, and lacking teeth. The variation in the relative length of pereopods 2-5 are given in Table 1 View TABLE 1 . The new species, however can be easily distinguished from its congeners by its prominent first two anterolateral teeth, much larger in size compared to the last two (the last tooth may be missing or greatly reduced in some specimens), and by the unique characteristics of the G1. The basal parts of the G1 of the new species bear a thick, mammillate tooth near the extremity of the ventral portion. These portions are unarmed or armed with tubercles in congeners. The distal portion bears a thick, mammillate ventral tooth which, in congeners, is absent. Some variations in the G1s of P. bidens new species are shown in figs. 3D–F and 4B–D.