Uroptychus sibogae Van Dam, 1933

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 30 (212)), pp. 1-612 : 481-484

Uroptychus sibogae Van Dam, 1933

Figure 241

Uroptychus sibogae Van Dam, 1933: 28 , figs 39-41. — Baba 1981: 119, fig. 6; 1988:45, fig. 17.

Not Uroptychus sibogae Poore et al. 2011: 330 , pl. 8, fig. A (= U.nebulosus n. sp.).

TYPE MATERIAL — Holotype: Indonesia, West of Manado , Celebes, 1901 m, male, ( ZMA De.101.665 ). [not examined].

MATERIAL EXAMINED — Philippines. MUSORSTOM 2 Stn CP15, 13°55’N, 120°29’E,326-330 m, 21.XI.1980, 2 ♂ 5.8,7.2 mm, 2 ov.♀ 6.2,6.7 mm (MNHN-IU-2014-16948) . MUSORSTOM 3 Stn CP97, 14°00’N, 120°18’E, 189-194 m, 1.VI.1985, 1 ♀ 3.8 mm (MNHN-IU-2014-16949) . Indonesia, Kai Islands. KARUBAR Stn CP16,5°17’S, 132°50’E,315-349 m, 24.X.1991,5 ♂ 7.0-8.5 mm,5 ov.♀ 6.7-7.9 mm (MNHN-IU-2014-16950) . – Stn CP27, 5°33’S, 132°51’E, 304-314 m, 26.X.1991, 1 ♂ 6.9 mm (MNHN-IU-2014-16951) . – Stn DW32, 5°47’S, 132°51’E, 170-206 m, 26.X.1991, 1 ♂ 5.2 mm, 1 ov. ♀ 5.9 mm (MNHN-IU-2014-16952) . Tanimbar Islands. KARUBAR Stn CP46, 8°01’S, 132°51’E, 271-273 m, 29.X.1991, 3 ♂ 4.7-6.8 mm, 1 ov. ♀ 6.4 mm (MNHN-IU-2014-16953) . Wallis and Futuna. MUSORSTOM 7 Stn CP606, 13°21,4’S, 176°08,3’ W, 420-430 m, 26 May 1992, 1 ♀ 4.2 mm (MNHN- IU-2010-5426) .

DISTRIBUTION„ West of Manado (Celebes [Sulawesi]), Molucca Sea off west coast of Halmahera, and Japan (Izu Shoto) in 170-1901 m, and now from the Philippines (off west coast of Luzon) and Indonesia (Kai and Tanimbar Islands), in 170- 349 m.

SIZE„ Males, 3.8-8.5 mm; females, 5.9-7.9 mm; ovigerous females from 5.9 mm.

DESCRIPTION„ Medium-sized species. Carapace: As long as broad; greatest breadth 1.3-1.5 × distance between anterolateral spines. Dorsal surface smooth and glabrous, slightly convex from anterior to posterior, with feeble depression between gastric and cardiac regions. Lateral margins medially convex (in small specimens) or convexly somewhat divergent posteriorly, bearing relatively small or moderate-sized anterolateral spine and another spine of same or slightly larger size at anterior end of branchial margin, followed by 5-7 tubercles or denticle-like small spines (often obsolescent). Rostrum broad triangular (distally narrower in small specimens), with interior angle of 25°-35°; dorsal surface concave; length 0.4-0.6 × that of carapace (longer in small specimens), breadth half carapace breadth at posterior carapace margin. Lateral orbital spine distinctly smaller than and situated anterior to level of anterolateral spine. Pterygostomian flap anteriorly roundish with very small spine on anterior margin, smooth on surface.

Sternum: Excavated sternum anteriorly ending in sharp spine, surface with small spine or low process in center. Sternal plastron very slightly shorter than broad, lateral extremities gently divergent posteriorly. Sternite 3 well depressed, anterior margin narrowly and deeply excavated, with 2 well-developed submedian spines nearly contiguous or separated by narrow notch, anterolaterally rounded. Sternite 4 having anterolateral margin relatively long, about 3 × as long as posterolateral margin, moderately convex, anteriorly ending in anteriorly or anterolaterally directed spine occasionally followed by a few posteriorly diminishing tubercles. Anterolateral margin of sternite 5 anteriorly convex and denticulate, 1.5 × longer than posterolateral margin of sternite 4.

Abdomen: Somites smooth and glabrous. Somite 1 slightly convex from anterior to posterior. Somite 2 tergite 2.4- 2.6 × broader than long; pleuron anterolaterally blunt angular, posterolaterally angular, lateral margin concavely strongly divergent posteriorly. Pleuron of somite 3 with angular lateral terminus. Telson 0.60-0.65 × as long as broad; posterior plate 1.5-1.8 × longer than anterior plate, posterior margin emarginate.

Eye: 1.5-1.8 × longer than broad, overreaching midlength of, but not reaching apex of rostrum; mesial margins concave (strongly so in small specimens). Cornea dilated (more distinctly in small specimens), about half as long as remaining eyestalk.

Antennule and antenna: Distal 2 articles of antennular peduncle relatively bulky, ultimate article 1.7-2.1 × longer than high. Antennal peduncle terminating in corneal margin. Article 2 with small lateral spine. Antennal scale barely reaching distal end of article 5, breadth 1.7-1.8 × that of article 5. Article 5 with small distomesial spine, length 2.4-3.0 × that of article 4, breadth 0.4 × height of ultimate antennular article. Flagellum of 21-24 segments reaching or slightly falling short of distal end of P 1 merus.

Mxp: Mxp1 with bases nearly contiguous. Mxp3 basis with 3 denticles on mesial ridge, proximal 2 often obsolete. Ischium with 18-25 denticles on crista dentata, flexor margin distally not rounded. Merus twice as long as ischium, unarmed or with vestigial distolateral spine; flexor margin well ridged, fringed with long setae; mesial face flattish. Carpus with very small or obsolescent distolateral spine.

P 1: Massive in large males, nearly glabrous except for distal articles, length 4.5-4.8 × that of carapace. Ischium dorsally with depressed triangular spine, ventrally unarmed. Merus 1.1-1.2 × longer than carapace, granulose on ventral surface. Carpus granulose on ventral surface, 1.1-1.2 × longer than merus. Palm 1.9-3.0 × (males), 2.3-2.4 × (females) longer than broad, slightly shorter than or subequal to carpus; breadth subequal to distance between lateral orbital spines in females and small males, occasionally more than that in large males; ventral surface smooth. Fingers slightly or moderately gaping (opposable margins fitting to each other in distal third, with proximal process of movable finger bidentate, located proximal to level of opposite low process on fixed finger) or strongly gaping (opposable margins fitting to each other in distal fifth of length, movable finger with relatively small blunt process in gaping margin, no process on opposable margin of fixed finger), crossing distally; movable finger 0.5-0.6 × length of palm (relatively long in small specimens, irrespective of sex).

P 2-4: Relatively slender, compressed mesio-laterally, with sparse long setae. Meri subequal on P 2 and P 3 or slightly longer (in large specimens) or slightly shorter (in small specimens) on P 3 than on P 2; length-breadth ratio, 4.9-6.0 on P 2, 4.7-6.0 on P 3, 4.2-5.5 on P 4 (broader in large specimens); breadths subequal on P 2 and P 3 or slightly larger on P 3 than on P 2; dorsal margin unarmed, ventrolateral margin with small distal spine; P 2 merus subequal to length of carapace, 1.4 × longer than P 2 propodus; P 3 merus 1.3 × length of P 3 propodus; P 4 merus 0.7-0.8 × length and 0.8 × breadth of P 3 merus, subequal to length of P 4 propodus. P 2 carpus subequal to P 3 carpus, P 4 carpus 0.8-0.9 × length of P 3 carpus; carpus-propodus length ratio, 0.6 on P 2, 0.5 on P 3 and P 4, distinctly longer than dactyli (carpus-dactylus length ratio, 1.6-1.7 on P 2, 1.5-1.7 on P 3, 1.2-1.3 on P 4); extensor margin with small distal spine at least on P 2 (obsolescent in small specimens). Propodi shortest on P 2, longest on P 3; flexor margin nearly straight, ending in pair of spines (very close to juncture with dactylus) preceded by row of 9-10 relatively long movable spines on P 2 and P 3, 7-8 spines on P 4 (located on distal three-quarters on P 2, slightly more distal on P 3 and P 4). Dactyli 0.3-0.4 × as long as propodi on P 2-4, shorter than carpi (dactylus-carpus length ratio, 0.6 on P 2, 0.6-0.7 on P 3, 0.8 on P 4); flexor margin curving at proximal third, ending in strong spine preceded by 8-9 similar spines diminishing toward base of article, ultimate spine strongest, penultimate slightly closer to ultimate than to antepenultimate on P 2, equidistant between on P 3 and P 4.

Eggs. Eggs carried 30 in number; size, 1.11 mm × 1.16 mm - 1.37 mm × 1.53 mm.

REMARKS„ The species strongly resembles U. longicarpus n. sp. and U. nebulosus n. sp. Characters distinguishing these species are outlined under the remarks of U. nebulosus (see above).