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: 502-506
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Uroptychus stenorhynchus n. sp.
Uroptychus sp. — Poore et al. 2011: 330, pl. 8, fig. H.
TYPE MATERIAL — Holotype: Vanuatu. MUSORSTOM 8 Stn CP 1051, 16°36.63’S, 167°59.90’E, 558- 555 m, 1.X.1994, ♂ 7.2 mm ( MNHN-IU-2014-16968)GoogleMaps . Paratypes: Vanuatu. MUSORSTOM 8 Stn CP974, 19°21.51’S, 169°28.26’E, 492- 520 m, 22.IX.1994, 1 ♂ 5.8 mm (MNHN-IU-2014-16969)GoogleMaps . – Stn CP 1051, station data as for the holotype, 1 ♂ 5.1, 2 ov. ♀ 5.7, 5.8 mm, 1 ♀ 5.0 mm (MNHN-IU-2014-16970).GoogleMaps SANTO Stn AT 73, 15°40.8’S, 167°00.5’E, 514-636 m, 07.X.2006, 1 ov. ♀ 6.0 mm (MNHN-IU-2014-16971)GoogleMaps . – Stn AT10, 15°41.1’S, 167°00.5’E, 509-659 m, 17.IX.2006, 1 ov. ♀ 7.1 mm ( MNHN- IU-2014-16972)GoogleMaps . – Stn AT19, 15°40.8’S, 167°00.5’E, 503-600 m, 21.IX.2006, 1 ♂ 6.0 mm (MNHN-IU-2014-16973)GoogleMaps .
ETYMOLOGY„ From the Greek stenos (narrow) and rhynchus (rostrum) referring to the narrow rostrum of the new species.
DISTRIBUTION„ Vanuatu; 492- 659 m.
SIZE„ Males, 5.1-7.2 mm; females, 5.0- 7.1 mm; ovigerous females from 5.7 mm.
DESCRIPTION„ Medium-sized species. Carapace: 1.1-1.2 × longer than broad; greatest breadth 1.7 × distance between anterolateral spines. Dorsal surface smooth and glabrous, moderately convex from anterior to posterior, smoothly sloping down to rostrum, bearing weak depression between gastric and cardiac regions; epigastric region with pair of denticulate ridges (obsolescent in small paratypes) behind eyes. Lateral margins slightly convexly divergent posteriorly, occasionally with slight constriction about at midlength; anterolateral spine stout, directed straight forward, overreaching small lateral orbital spine; with 2 eminences or small spines, one on anterior end of anterior branchial margin and another on anterior end of posterior branchial margin. Rostrum horizontal, narrow triangular, with interior angle of 20°; length slightly less than half that of remaining carapace, breadth less than half carapace breadth at posterior carapace margin; dorsal surface flattened. Lateral orbital spine slightly anterior to level of, and separated from anterolateral spine by basal breadth of that spine. Pterygostomian flap smooth on surface, anteriorly angular and pointed.
Sternum: Excavated sternum produced to spine between bases of Mxp1, surface with low process or spine in center. Sternal plastron about as long as broad, lateral extremities gently divergent posteriorly. Sternite 3 strongly depressed, anterior margin broadly and deeply excavated, with pair of submedian spines without distinct notch between. Sternite 4 also depressed medially; anterolateral margin slightly convex, anteriorly ending in short spine followed by small or denticlelike, posteriorly diminishing spines, length about twice that of posterolateral margin. Anterolateral margin of sternite 5 nearly subparallel, anteriorly rounded, slightly longer than posterolateral margin of sternite 4.
Abdomen: Smooth and glabrous. Somite 1 with antero-posteriorly convex, well-elevated transverse ridge. Somite 2 tergite 2.3-2.5 × broader than long; pleuron posterolaterally blunt, lateral margin concavely moderately divergent posteriorly. Pleuron of somite 3 with bluntly angular lateral terminus. Telson 0.6-0.7 × as long as broad; posterior plate 1.2-1.4 × longer than anterior plate, posterior margin slightly emarginate.
Eye: Broad relative to length, 1.7 × longer than broad, reaching point distal third of rostrum; mesial and lateral margins subparallel. Cornea not inflated, length slightly less than half that of eyestalk.
Antennule and antenna: Ultimate article of antennule 2.0-2.5 × longer than high. Antennal peduncle terminating in or slightly overreaching corneal margin. Article 2 with well-developed distolateral spine. Antennal scale slightly falling short of distal end of peduncle, 1.2 × broader than article 5. Distal 2 articles unarmed; article 5 2.2-2.7 × longer than article 4; breadth at most half height of ultimate article of antennule. Flagellum of 11-15 segments slightly falling short of distal end of P 1 merus.
Mxp: Mxp1 with bases close to each other. Mxp3 glabrous on lateral surface. Basis with 3-4 denticles on mesial ridge. Ischium having flexor margin not rounded distally, crista dentata with about 15 denticles. Merus twice as long as ischium, flattish on mesial face, flexor margin moderately ridged. No spine on merus and carpus.
P 1: Massive in largest male (holotype), not so in all paratypes, 4.3-4.7 × longer than carapace in both sexes, bearing setae only on fingers. Ischium with short procurved dorsal spine; ventromesial margin with a few denticle-like proximal processes, subterminal spine vestigial (holotype) or absent (paratypes). Merus with row of 4-5 small spines on proximal mesial margin and small tubercle-like spines on ventral surface; length 1.0-1.1 × that of carapace. Carpus unarmed, 1.2- 1.4 × longer than merus. Palm also spineless, relatively high dorsoventrally, 1.7-2.8 × (males), 2.5-3.1 × (females) longer than broad, as long as or slightly shorter than carpus. Fingers distally crossing, largely gaping in largest male (holotype), slightly so in other male paratypes and large females, not gaping in females; movable finger half as long as palm, opposable margin with obtuse proximal process (situated at midlength of gaping portion in largest male holotype).
P 2-4: Moderately compressed mesio-laterally, setose on distal 2 articles, sparsely so on carpi, barely so on meri, setae on carpi and propodi long. Meri subequal in length and breadth on P 2 and P 3 (rarely slightly longer on P 3), much shorter and narrower on P 4 ( P 4 merus 0.6-0.7 × length of, 0.7 × breadth of P 3 merus); length-breadth ratio, 4.2-4.7 on P 2, 4.1-4.6 on P 3, 3.7-3.9 on P 4; dorsal margin roundly ridged and unarmed. P 2 merus 0.9 × length of carapace, 1.0-1.2 × length of P 2 propodus; P 3 merus 1.1 × length of P 3 propodus; P 4 merus 0.9-1.0 × length of P 4 propodus. Carpi subequal on P 2-3, shorter on P 4 ( P 4 carpus 0.7-0.8 × length of P 3 carpus), distinctly longer than dactyli (carpus-dactylus length ratio, 1.6- 1.7 on P 2, 1.4-1.5 on P 3, 1.1-1.2 on P 4); carpus-propodus length ratio, 0.5-0.6 on P 2, 0.5 on P 3 and P 4. Propodi longest on P 3, shortest on P 4 or subequal on P 2 and P 4; flexor margin nearly straight, with single terminal spine slightly distant from juncture with dactylus, preceded by 6-7 ( P 2 and P 3) or 5 ( P 4) movable spines. Dactyli proportionately broad, strongly curving at proximal third; shorter than carpi, dactylus-propodus length ratio, 0.4 on P 2 and P 3, 0.4-0.5 on P 4; flexor margin with 8-9 proximally diminishing, somewhat inclined sharp spines, ultimate largest or subequal to penultimate.
Eggs. Eggs carried, 16-28 in number; size, 1.05 mm × 0.98 mm - 1.16 mm × 1.18 mm.
Color. Male from SANTO AT19 (MNHN-IU-2014-16973), Vanuatu: Carapace and appendages pale pink; distal articles of P 2-4 more or less orangish; abdomen translucent white. This specimen was shown in Poore et al. (2011).
REMARKS„ The elongate carapace, shapes of the pterygostomian flap and sternum, the length ratio of P 2-3 carpi to dactyli, and the spination of the P 2-4 dactyli displayed by U. stenorhynchus resemble those of U. lacunatus n. sp. (see above). Their differences are very small but U. stenorhynchus is distinguished from that species by the more narrowly elongate rostrum, the antennal article 2 bearing a strong instead of small distolateral spine, and the P 2-4 propodi bearing a single instead of paired terminal spines on the flexor margin.
Uroptychus stenorhynchus also resembles U. dejouanneti n. sp. (see above) in having the P 2-4 propodi with the distalmost of the flexor terminal marginal spines single and not paired, and the dactyli with sharply triangular, obliquely directed flexor marginal spines, the distal two of which are subequal. Uroptychus stenorhynchus is more largely different from U. dejouanneti than from U. lacunatus : the rostrum is narrower, distinctly overreaching the eyes; the anterolateral spine of the carapace is well developed instead of small, distinctly overreaching instead of terminating at most in the tip of the lateral orbital spine; the antennal article 2 bears a well-developed instead of very tiny distolateral spine; and the P 4 merus is 0.6-0.7 instead of 0.9 times as long as the P 3 merus. In addition, P 1-4 are broader relative to length.
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