Uroptychus litosus Ahyong & Poore, 2004

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 : 270-272

Uroptychus litosus Ahyong & Poore, 2004

Figure 125

Uroptychus litosus Ahyong & Poore, 2004: 52 , fig. 14. — Poore 2004: 226, figs 60f, 62g (compilation). — Baba 2005: 227 (synonymies, key).

TYPE MATERIAL — Holotype: Australia, “Andys” Seamount, 65.5 km SSE of SE Cape, 44°10.8´S, 147°00.0´E, 800 m, male ( NMV J52862 ). [not examined].

MATERIAL EXAMINED — Wallis and Futuna Islands. MUSORSTOM 7 Stn CP638, 13°37’S, 179°56’E, 820-840 m, 30.V.1992, 1 ♂ 9.3 mm ( MNHN- IU-2014-16618) , 1 ♂ 7.9 mm, 1 ov. ♀ 9.3 mm (MNHN-IU-2014-16619) . Solomon Islands. SALOMON 2 Stn CP2297, 9°08.8’S, 158°16.0’E, 728-777 m, 8.XI.2004, 1 sp. (sex indet.) 7.6 mm (MNHN-IU-2014-16620).

DISTRIBUTION„ Southern Tasmania, and now Wallis and Futuna Islands and Solomon Islands; 728-1120 m.

DESCRIPTION„ Medium-sized species. Carapace: as long as broad; greatest breadth 1.7-1.8 × distance between anterolateral spines. Dorsal surface smooth and glabrous, somewhat convex from anterior to posterior, with shallow depression between gastric and cardiac regions. Epigastric region with pair of tuberculate ridges behind eyes. Lateral margins convexly divergent, bearing tubercles; low ridge along posterior fourth; anterolateral spine well developed, overreaching lateral orbital spine. Rostrum sharp triangular, with interior angle of 25-30°, horizontal, dorsal surface flattish; length 0.4 × postorbital carapace length, breadth about half carapace breadth at posterior carapace margin. Lateral orbital spine small, moderately remote from and anterior to level of anterolateral spine. Pterygostomian flap anteriorly angular, produced to distinct spine, surface smooth and glabrous.

Sternum: Excavated sternum sharply produced between bases of Mxp1, surface with spine in center. Sternal plastron 0.9 × as long as broad, sternites successively broader posteriorly. Sternite 3 depressed well, anterior margin in broad V-shape with 2 submedian spines separated by shallow, narrow notch; anterolaterally sharp angular. Sternite 4 with anterolateral margin convex, irregular and somewhat crenulated, anteriorly produced to blunt spine reaching submedian spines of sternite 3; posterolateral margin half as long as anterolateral margin. Anterolateral margin of sternite 5 convex, slightly longer than posterolateral margin of sternite 4.

Abdomen: Tergites smooth and glabrous. Somite 1 pronouncedly convex from anterior to posterior. Somite 2 tergite 2.5-2.8 × broader than long; pleuron with concavely divergent lateral margin, bluntly produced posterolaterally. Pleuron of somite 3 with bluntly angular lateral margin. Telson 0.5-0.6 × as long as broad; posterior plate 1.3-1.5 × (males), 1.7 (female) longer than anterior plate, posterior margin somewhat concave.

Eye: Short relative to breadth (1.5 × longer than broad), overreaching midlength of, but not reaching distal end of rostrum, mesial margin concave. Cornea slightly dilated, more than half as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 2.3-2.8 × longer than high. Antennal peduncle overreaching cornea. Article 2 with strong lateral spine. Antennal scale slightly falling short of distal end of article 5, slightly overreaching cornea, breadth slightly more than 2 × that of article 5. Distal 2 articles unarmed. Article 5 1.8-2.3 × longer than article 4, breadth 0.4-0.5 × height of antennular ultimate article. Flagellum consisting of 18-20 segments, slightly falling short of or reaching distal end of P1 merus.

Mxp: Mxp1 with bases close to each other. Mxp3 basis with 4 denticles on mesial ridge. Ischium with about 20 denticles on crista dentata, flexor margin distally not rounded. Merus 2 × longer than ischium, unarmed, flexor margin not cristate but roundly ridged. Carpus also unarmed.

P1: Missing in female. Male P1 3.8-4.8 × longer than carapace, massive, barely setose on merus, sparsely so on carpus and palm, thickly so on fingers. Ischium with procurved dorsal spine, ventrally with a few denticle-like small spines on mesial margin, lacking subterminal spine. Merus ventrally granulose, with or without row of tubercle-like spines on mesial and ventromesial margins; length 1.0-1.2 × that of carapace. Carpus 1.2-1.3 × longer than merus. Palm rounded on mesial margin, 2.0 × longer than broad, 0.8-0.9 × length of carpus. Fingers distally incurved, crossing when closed; movable finger 0.6-0.7 × length of palm, opposable margin with 2-toothed process on proximal portion; opposable margin of fixed finger with low angular prominence distal to midlength.

P2-4: With setae sparse on meri and carpi, numerous on propodi and dactyli; setae on distal parts of carpi and propodi long, those on dactyli short. Meri successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.8 × length of P3 merus); P2-3 meri subequal in breadth, P4 merus 0.9 × as broad as P3 merus; dorsal margins with obsolescent eminences on proximal half on P2, smooth on P3 and P4; length-breadth ratio, 4.8-5.5 on P2, 4.6-5.0 on P3, 4.0-4.2 on P4; P2 merus 0.8-1.0 × length of carapace, 1.1-1.2 × length of P2 propodus; P3 merus 1.1 × length of P3 propodus; P4 merus 0.9 × length of P4 propodus. Carpi subequal in length on P2 and P3 or slightly shorter on P3 than on P2; P4 carpus 0.9 × length of P3 carpus; carpus-propodus length ratio 0.6 on P2, 0.5-0.6 on P3 and P4. Propodi subequal in length on P2 and P3, slightly shorter on P4; flexor margin somewhat convex distally, with pair of terminal spines preceded by row of 7 or 8 movable slender spines on proximal half on P2, 6-7 spines on P3, 5-7 spines on P4. Dactyli successively longer posteriorly, much shorter than carpi (dactylus-carpus length ratio, 0.6 on P2, 0.6-0.7 on P3, 0.7-0.8 on P4), slightly more than one-third length of propodi (0.36-0.37 on P2, 0.35-0.38 on P3, 0.36-0.40 on P4); flexor margin with 10-12 triangular spines somewhat obliquely directed, loosely arranged and diminishing toward base of article, ultimate, penultimate and antepenultimate subequal.

Eggs. Number of eggs carried, 4 (normal number probably more); size, 1.5 mm × 1.73 mm - 1.58 mm × 1.85 mm.

REMARKS — This species has convexly divergent, spineless (other than the anterolateral spine) lateral margins of the carapace, relatively massive P1, relatively long P2-4 carpi, and proximally diminishing triangular spines on the flexor margin of the P2-4 dactyli, characters shared by U. acostalis Baba, 1988 , U. bardi McCallum & Poore, 2013 , and U. orientalis Baba & Lin, 2008 . Uroptychus litosus differs from U. acostalis in having a pair of denticulate ridges on the epigastric region, in having sternite 4 with the anterolateral angle not so strongly produced as to reach the anterior margin of sternite 3, and in having the P1 ischium with a strongly procurved instead of very short triangular spine on the dorsal side. Distinctions between U. litosus and U. bardi are noted under the remarks of that species (see above). The relationships with U. orientalis have been discussed by Baba & Lin (2009).

The species also resembles U. anacaena Baba & Lin, 2008 in the spination of the P2-4 dactyli and in the carapace shape, but it differs in having the carapace dorsal surface smooth except for a pair of tuberculate epigastric ridges instead of being totally granulose, in having the anterolateral margin of sternite irregular rather than smooth, and in having the P2-4 dactyli much shorter than instead of equally long as the carpi.

Figures

FIGURE 125 Uroptychus litosus Ahyong & Poore,2004,male 9.3 mm (MNHN-IU-2014-16618).A,carapace and anterior part of abdomen,proximal part of right P1 included, dorsal. B, same, lateral.C, sternal plastron, with excavated sternum and basal parts of Mxp1. D, telson. E, left antenna,ventral.F, left Mxp3,ventral.G, right P1,proximal articles omitted,dorsal.H, left P2,lateral.I, same,distal part,setae omitted, lateral. Scale bars: A, B, G,H, 5 mm; C- F, I, 1 mm.