Uroptychus thermalis Baba & de Saint Laurent, 1992

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 : 518-522

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Uroptychus thermalis Baba & de Saint Laurent, 1992


Uroptychus thermalis Baba & de Saint Laurent, 1992

Figures 261-263 View FIGURE 261 View FIGURE 262 View FIGURE 263

Uroptychus thermalis Baba & de Saint Laurent, 1992: 324 , fig. 2. — Chevaldonné & Olu 1996: 293. — Ahyong & Poore 2004 a: 77, fig. 24. — Baba 2005: 231.

TYPE MATERIAL — Holotype: North Fiji Basin, 16°59.50’S, 173 °55.47’W, hydrothermal vent, 2000 m, male ( MNHN-Ga 2351 ). [examined]. GoogleMaps

MATERIAL EXAMINED — New Caledonia. BIOCAL Stn CP72, 22°10’S, 167°33’E, 2100-2110 m, 4.IX.1985, 1 ♀ 8.1 mm (MNHN-IU-2014-16988) .

DISTRIBUTION„ North Fiji Basin (active thermal vent site), Queensland, and now New Caledonia; 1497-2110 m.

DIAGNOSIS„ Medium-sized species. Carapace slightly longer than broad; greatest breadth 1.6 × distance between anterolateral spines. Dorsal surface with elevated, granulate, short ridges; gastric and cardiac regions distinctly bordered by deep groove, and both well inflated; anterolateral spine directed anterolaterally, overreaching angular lateral limit of orbit, followed by no spine but a row of short granulate ridges along branchial margin. Rostrum narrow triangular, with interior angle of 22-26°; breadth half length of posterior carapace margin; dorsal surface smooth, slightly convex from side to side. Pterygostomian flap with roundish anterior margin bearing small spine. Excavated sternum anteriorly convex with small spine, surface with small central spine; sternal plastron 1.2 × broader than long; lateral extremities divergent posteriorly; sternite 3 depressed, anterior margin moderately concave, with pair of small submedian spines; sternite 4 with strong spine about at midlength of anterolateral margin, posterolateral margin as long as anterolateral margin; sternite 5 with anterolateral margin straightly divergent posteriorly, slightly more than half as long as posterolateral margin of sternite 4. Abdomen smooth and glabrous, somite 1 strongly convex from anterior to posterior; somite 2 tergite 2.0 × broader than long; pleuron having lateral margin concavely strongly divergent posteriorly, ending in blunt tip; pleuron of somite 3 blunt on lateral terminus. Telson three-fifths as long as broad; posterior plate subsemicircular, posteriorly rounded, length 1.7 × that of anterior plate. Eyes short relative to breadth; cornea inflated, as long as remaining eyestalk. Ultimate article of antennular peduncle 2.5 × longer than high. Antennal peduncle slender, overreaching cornea; article 2 with small lateral spine; antennal scale slightly overreaching article 4; distal 2 articles unarmed, article 5 twice as long as article 4, breadth less than half height of ultimate article of antennule; flagellum of 10 or 11 segments far falling short of distal end of P 1 merus. Mxp1 with bases close to each other. Mxp3 slender and spineless; coxa with strong ventral spine; basis with 1 denticle on distal part of mesial ridge; ischium having flexor margin not rounded distally, crista dentata with obsolescent denticles; merus 2.8 × longer than ischium, relatively thick mesio-laterally; carpus longer than ischium. P 1 slender; ischium with small dorsal process, ventrally unarmed; merus with 2 prominent distodorsal spines, length 1.4 × that of carapace; carpus 1.5 × longer than merus, with 1 distodorsal and 1 lateral distoventral spine; palm 0.8 × length of carpus; fingers spooned on prehensile face, not crossing distally when closed; movable finger 0.6 × as long as palm; fixed finger with median process opposite to between 2 proximal processes of movable finger. P 2-4 slender, subcylindrical on meri and carpi, sparsely setose on distal articles; meri subequally broad on P 2-4, unarmed; P 2 merus slightly longer than carapace, 1.7 × longer than P 2 propodus; P 3 merus 0.9 × length of P 2 merus; P 4 merus 0.9 × length of P 3 merus, slightly longer than P 4 propodus; carpi long, subequal in length on P 2 and P 3, slightly shorter on P 4 than on P 2 and P 3, carpus-propodus length ratio, 1.0 on P 2, 0.8 on P 3 and P 4; propodi broadened medially; flexor margin with slender movable spines distal to midlength, distalmost single, slightly proximal to juncture with dactylus, distantly separated from proximal group of 4-5 spines; dactyli strongly curving, 0.4 × as long as propodi on P 2-4, and 0.4 × as long as carpi on P 2 and P 3, 0.5 × on P 5, flexor margin with terminal and subterminal spines of good size (subterminal spine absent in this specimen), both remotely separated from proximal group of 6 very small obliquely directed spines.

REMARKS„ No clear differences were found in the relative lengths of articles of P 2-4 between the type and the present material. Apparently this female specimen is identical with the male reported by Ahyong & Poore (2004) from a non-vent site in Queensland, sharing the presence of a strong lateral spine on sternite 4, two distodorsal spines on the P 1 merus and one distodorsal spine on the P 1 carpus. In the type material, the lateral spine of sternite 4 is very small, the P 1 merus bears one instead of two spines, and the P 1 carpus has no distodorsal spine. Ahyong & Poore (2004) considered these differences as age-related variations, but the present specimen is about as large as in the type material. The crista dentata of the Mxp3 ischium in this specimen bears denticles more obsolescent than in the type. Given that the type material was taken from the active thermal vent-site, the material from Queensland and New Caledonia may be referable to a different species. However, this is provisionally placed in U. thermalis , pending a discovery of additional material from the type locality and molecular analyses.

The spination of the P 2 dactylus is illustrated here for the BIOCAL specimen; the small spines on the proximal portion are also discernible under high magnification in the type ( Figure 263E View FIGURE 263 ). Dactylar and propodal spination of the P 2-4 are similar between U. thermalis and U. sternospinosus Tirmizi, 1964 , as also are the slender pereopods, short antennal scales, and the shape of the sternal plastron. In U. sternospinosus , however, the P 2-4 carpi are consistently longer than the propodi, and the carapace bears a distinct longitudinal carina in midline and a pair of strong gastric spines, the characters confirmed by examination of the type material ( BMNH 1966.2.3.21-22).














Uroptychus thermalis Baba & de Saint Laurent, 1992

Baba, Keiji 2018

Uroptychus thermalis

BABA K. 2005: 231
CHEVALDONNE P. & OLU K. 1996: 293