Uroptychus salomon, Baba, 2018

Baba, Keiji, 2018, Chirostylidae of the Western and Central Pacific: Uroptychus and a new genus (Crustacea: Decapoda: Anomura), Tropical Deep-Sea Benthos (Mémoires du Muséum national d'Histoire naturelle 212), pp. 1-612 : 447-450

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Uroptychus salomon

n. sp.

Uroptychus salomon n. sp.

Figures 223 View FIGURE 223 , 224 View FIGURE 224

TYPE MATERIAL — Holotype: Solomon Islands. SALOMON 2 S tn CP2197, 8°24.2’S, 159°22.5’E, 897-1057 m, 24.X.2004, ov. ♀ 8.4 mm ( MNHN-IU-2014-16939 ) GoogleMaps . Paratypes: station data as for the holotype, 1 ♂ 5.2 mm, 1 ov. ♀, 7.8 mm (MNHN-IU-2014-16940).

ETYMOLOGY„ Named for the cruise SALOMON 2, by which the type material of this species was collected; used as a noun in apposition.

DISTRIBUTION„ Solomon Islands; 897-1057 m.

DESCRIPTION„ Medium-sized species. Carapace: As long as broad; greatest breadth 1.9 × distance between anterolateral spines. Dorsal surface smooth and glabrous, slightly convex from anterior to posterior, anteriorly smoothly sloping down to rostrum, with feeble depression between gastric and cardiac regions. Lateral margins moderately convex posteriorly, with 2 spines; first anterolateral spine small, reaching or slightly overreaching much smaller lateral orbital spine; second spine smaller than anterolateral spine, situated at anterior end of branchial region, followed by row of several short oblique ridges; distinctly ridged along posterior half of branchial margin. Rostrum long triangular, with interior angle of 21-25°; dorsal surface flattish, straight horizontal; ventral surface directed somewhat dorsally in profile; lateral margin entire; length slightly less than half (0.45-0.47 x) that of remaining carapace, breadth less than half carapace breadth at posterior carapace margin. Lateral orbital spine slightly anterior to level of and moderately remote from anterolateral spine. Pterygostomian flap smooth on surface, anterior margin roundish but slightly angular at anterior end bearing very small spine.

Sternum: Excavated sternum anteriorly sharp triangular, surface with longitudinal ridge in midline around center. Sternal plastron as long as or slightly shorter than broad, lateral extremities gently divergent posteriorly. Sternite 3 strongly depressed; anterior margin well concave, with small median notch flanked by small spine (with 1 or 2 small accompanying spines lateral to each in holotype). Sternite 4 with granulate transverse ridge on surface; anterolateral margin as long as posterolateral margin, anteriorly ending in small spine, somewhat convex medially bearing a few to several denticles. Sternite 5 short, length less than half (0.4) that of sternite 4; anterolateral margins somewhat convex and irregular, posteriorly divergent, length 0.4 × that of posterolateral margin of sternite 4.

Abdomen: Tergites smooth and glabrous. Somite 1 well convex from anterior to posterior. Somite 2 tergite 2.1-2.5 × broader than long; pleuron anterolaterally rounded, posterolaterally bluntly angular; lateral margin concave and strongly divergent posteriorly. Pleuron of somite 3 with bluntly angular lateral terminus. Telson 0.6 × as long as broad; posterior plate 1.6 × longer than anterior plate, emarginate on posterior margin.

Eye: Short relative to breadth, 1.3-1.4 × longer than broad, proximally narrowed, slightly or distinctly overreaching midlength of rostrum. Cornea somewhat swollen, about as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 2.9-3.7 × longer than high. Antennal peduncle terminating in corneal margin. Article 2 with small lateral spine. Antennal scale slightly less than twice as broad as article 5, ending in midlength of that article. Distal 2 articles unarmed. Article 5 1.8-2.3 × longer than article 4, breadth 0.3-0.4 × height of antennular ultimate article. Flagellum of 12-16 segments not reaching distal end of P 1 merus.

Mxp: Mxp1 with bases close to each other. Mxp3 basis with 1 distal denticle on mesial ridge. Ischium with very small denticles on crista dentata; flexor margin distally not rounded. Merus 2.7 × longer than ischium, unarmed, moderately ridged along flexor margin. Carpus also unarmed.

P 1: Slender, especially merus and carpus, setose on fingers, sparsely so on palm, carpus and merus; length 4.6-5.9 × that of carapace. Ischium with short dorsal spine, ventromesially unarmed. Merus 1.2-1.5 × longer than carapace, unarmed. Carpus 12 × longer than broad, 1.3-1.4 × length of merus. Palm‰.7 × length of carpus, 3.7-4.8 × longer than broad. Fingers slightly gaping in proximal two-fifths in male, not gaping in females, distally ending in small incurved spine; movable finger 0.6-0.7 × that of palm, opposable margin with obtuse proximal process.

P 2-4 slender, relatively thick mesio-laterally, sparsely setose except for distal part. Meri successively shorter posteriorly ( P 3 merus 0.9 × length of P 2 merus, P 4 merus 0.9 × length of P 3 merus); equally broad on P 2-4; length-breadth ratio, 8.7-9.3 (females) or 7.3 (male) on P 2, 7.5-8.3 (females) or 6.4 (male) on P 3, 6.6-7.2 (females) or 5.8 (male) on P 4; dorsal margin unarmed; ventrolateral margin with terminal spine; P 2 merus about as long as (females) or slightly shorter (male) than carapace, 1.6 × longer than P 2 propodus; P 3 merus 1.4 × length of P 3 propodus; P 4 merus 1.0-1.2 × length of P 4 propodus. Carpi unarmed, P 3 carpus 0.95-0.96 × length of P 2 carpus, P 4 carpus 0.93-0.99 × length of P 3 carpus; much longer than dactyli (carpus-dactylus length ratio, 2.2-2.6 on P 2, 2.0-2.2 on P 3, 2.0-2.2 on P 4); carpus-propodus length ratio, 0.9-1.0 on P 2, 0.8-0.9 on P 3 and P 4. Propodi subequal in length on P 3 and P 4, shorter on P 2 (female holotype and male), or subequal on P 2 and P 3, longer on P 4 (female paratype); flexor margin straight, ending in pair of spines preceded by 7 or 8 slender movable spines in distal half on P 2, 6 or 7 spines on P 3, 6 spines on P 4. Dactyli 0.4 × length of carpi on P 2, 0.5 × on P 3 and P 4; strongly curving at proximal quarter, with 9 or 10 proximally diminishing, obliquely directed flexor marginal spines, ultimate subequal to or slightly larger than penultimate, antepenultimate closer to fourth than to penultimate on P 2, equidistant between on P 3 and P 4.

Eggs. Number of eggs carried, 8-16; size, 1.27 mm × 1.31 mm - 1.38 mm × 1.68 mm.

REMARKS„ The new species resembles U. politus ( Henderson, 1885) in the carapace shape and the spination of P 2-4, and in having the P 2-4 carpi much longer than the dactyli. However, U. salomon is distinguished from that species by the much more slender pereopods, especially P 1 that has the carpus 12 times instead of 2.6-4.0 times longer than broad; sternite 4 has the anterolateral margin as long as instead of 1.6-1.8 times longer than the posterolateral margin; sternite 5 is very short, 0.4 instead of 0.7-0.8 times as long as sternite 4, with the anterolateral margin less than half (0.4) instead of subequal to the length of the posterolateral margin of sternite 4; and the crista dentata of Mxp3 ischium bears distinct instead of obsolescent denticles.