Uroptychus turgidus, 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 : 539-543

Uroptychus turgidus n. sp.

Figures 272-274

TYPE MATERIAL — Holotype: New Caledonia, Chesterfield Islands . MUSORSTOM 5 Stn CP 278, 24°10.80’S, 159°38.10’E, 265 m, coral unidentified, 10.X.1986, ♂ 2.0 mm ( MNHN-IU-2014-17007 ) . Paratype: Collected with holotype, 1 ov. ♀ 1.9 mm (MNHN-IU-2014-17008).

ETYMOLOGY„ From the Latin turgidus (swollen), alluding to the dorsally swollen branchial region, characteristic of

the species.

DISTRIBUTION„ Chesterfield Islands; 265 m.

DESCRIPTION„ Small species. Carapace: Broader than long (0.8 × as long as broad); greatest breadth 1.6 × distance between anterolateral spines. Dorsal surface with sparse tufts of long soft setae on posterior half and relatively small spines of irregular sizes along lateral margin; posterior branchial regions markedly inflated, other portions nearly horizontal in profile. Lateral margins convex on branchial region, with spines of irregular sizes; anterolateral spine small, distinctly posterior to level of, but not reaching apex of lateral orbital spine; 2 somewhat larger spines on posterior branchial region, anterior one dorsal in position. Rostrum broad triangular, with interior angle of 45°, distally blunt; dorsal surface concave; length less than half that of carapace, breadth much more than half carapace breadth at posterior carapace margin. Lateral orbital spine well developed, much larger than anterolateral spine. Pterygostomian flap covered with spinules, anterior margin somewhat angular, produced to distinct spine.

Sternum: Excavated sternum anteriorly convex, bearing ridge in midline. Sternal plastron as long as broad; lateral extremities subparallel between sternites 5-7. Sternite 3 shallowly depressed, anterior margin representing broad V-shape, with narrow deep median notch, lacking submedian spines. Sternite 4 broadest among sternites; anterolateral margin smooth, with blunt anterior end, length subequal to that of posterolateral margin. Anterolateral margins of sternite 5 subparallel, anteriorly rounded, length 0.7 × that of posterolateral margin of sternite 4.

Abdomen: Sparsely setose. Somite 1 without transverse ridge. Somite 2 tergite 2.5 × broader than long; pleuron posterolaterally blunt, lateral margins feebly concave and subparallel. Pleuron of somite 3 with rounded lateral margin. Telson half as long as broad; posterior plate medially not expanded laterally, length 1.3 × that of anterior plate, posterior margin feebly concave.

Eye: 1.5 × longer than broad, distally narrowed, reaching apex of rostrum; lateral and mesial margins convex. Cornea about half as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 3.5-3.7 × longer than high. Antennal peduncle reaching apex of rostrum. Article 2 with strong distolateral spine. Antennal scale slightly overreaching midlength of article 5, 1.5 × broader than article 5. Article 4 with distomesial spine. Article 5 unarmed, slightly longer than article 4, breadth 0.6 × height of antennular ultimate article. Flagellum consisting of 13-14 segments, not reaching distal end of P1 merus.

Mxp: Mxp1 with bases moderately separated. Mxp3 with long soft setae on lateral surface. Basis without denticles on mesial ridge. Ischium with distally rounded flexor margin; crista dentata with obsolescent denticles. Merus 2.2 × longer than ischium, flattish, not strongly cristate but somewhat rounded on flexor margin, bearing well-developed distolateral spine. Carpus unarmed.

P1: 7 × longer than carapace, relatively slender, sparingly with long soft setae. Ischium dorsally with sharp long spine, ventromesially unarmed. Merus, carpus and palm unarmed, Merus 1.5-1.6 × longer than carapace. Carpus 1.2-1.3 × longer than merus, 0.8 × (male) or 1.0 × (female) as long as palm. Palm 4.2 × (male) or 6.5 × (female) longer than broad, 1.1 × (female) or 1.3 × (male) longer than carpus. Fingers relatively narrowed distally, curving ventrally, somewhat incurved distally, crossing when closed; in female, opposable margins nearly straight, without processes in female; in male, opposable margin of movable finger with 2 low processes, distal one at distal third, proximal one at proximal third and slightly proximal to position of opposite low process on fixed finger; movable finger about one-third length of palm.

P2-4: Relatively thick mesio-laterally, bearing long soft setae. Meri successively slightly shorter posteriorly (P3 merus 0.96-0.97 × length of P2 merus, P4 merus 0.86-0.95 × length of P3 merus), breadths subequal on P2-4; length-breadth ratio, 3.7-3.8 on P2, 3.5-3.6 on P3, 3.1-3.6 on P4; dorsal margin with 2 small proximal spines distinct on P2-4 (male holotype) or obsolescent on P2-4 (ovigerous paratype); P2 merus 0.8 × length of carapace as well as P2 propodus; P3 merus 0.7 × length of P3 propodus; P4 merus 0.7 length of P4 propodus. Carpi subequal, length 0.2-0.3 × that of propodi on P2-4, 0.6-0.7 × that of dactyli on P2, 0.6 × on P3 and P4. Propodi shortest on P2, longer and subequal on P3 and P4; flexor margin slightly concave in lateral view, with pair of terminal spines only. Dactyli subequal in length on P2-4, slightly less than half length of propodi (dactylus-propodus length ratio, 0.40-0.45 on P2, 0.40-0.43 on P3, 0.42-0.43 on P4); 1.6-1.7 × longer than carpi on P2 and P3, 1.6 × longer on P4; flexor margin nearly straight, with 6 or 7 spines, ultimate spine very slender and close to penultimate spine; penultimate spine strong, much broader and longer than remainder, twice as broad as antepenultimate, remaining spines loosely arranged and proximally diminishing, antepenultimate and fourth spines perpendicular to margin, fifth and sixth (and seventh where present) somewhat inclined, antepenultimate more distant from penultimate than from fourth.

Eggs. Number of eggs carried, 3; size, 0.88 mm × 1.05 mm - 0.88 mm × 1.15 mm.

REMARKS„ The combination of the following characters links the species to U. sarahae n. sp., U. toka Schnabel, 2009 and U. volsmar n. sp.: the small anterolateral spine of the carapace subequal to or smaller than the lateral orbital spine, sternite 3 with a distinct median notch on the anterior margin, the short antennal scale ending at most in the midlength of article 5, and the P2-4 dactyli with perpendicularly directed spines proximal to the prominent penultimate spine on the flexor margin. Uroptychus turgidus is readily distinguished from these species by the presence of the pronounced inflation on the posterior branchial region and a few distinct spines along its lateral margin.

Figures

FIGURE 272 Uroptychus turgidus n. sp., holotype, male 2.0 mm (MNHN-IU-2014-17007). A, carapace and anterior part of abdomen, dorsal. B, same, lateral. C, sternal plastron, with excavated sternum and basal parts of Mxp1. D, telson. E, left antenna, ventral.F, right Mxp3,ventral.G, left Mxp3,lateral.H, left P1, dorsal. Scale bars: 1 mm.

FIGURE 273 Uroptychus turgidus n. sp.,holotype,male 2.0 mm (MNHN-IU-2014-17007).A, right P2,lateral.B, same,distal part,setae omitted,lateral.C, left P3,setae omitted, lateral. D, left P4, setae omitted,lateral.Scale bars:1 mm.

FIGURE 274 Uroptychus turgidus n. sp. A, B, holotype, male 2.0 mm (MNHN-IU-2014-17007). C, D, paratype, ovigerous female 1.9 mm (MNHN-IU-2014-17008). A, carapace, left part, dorsolateral. B, same, anterolateral part, right, showing eye and lateral orbital spine, dorsal.C, P2, distal part, setae omitted, lateral.D, P4, distal part,setae omitted, lateral. Scale bars: 1 mm.