Uroptychus spinosior Baba 2018, n. sp.
Creators: name: Baba, Keiji
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Chirostylidae
Uroptychus
Uroptychus spinosior

description: Uroptychus spinosior n. sp.
Figures 246, 247
TYPE MATERIAL — Holotype: Wallis and Futuna Islands. MUSORSTOM 7 Stn DW 516, 14°13’S, 178°12’W, 441-550 m, 12.V.1992, ov. ♀ 3.5 mm (MNHN-IU-2011-5941). Paratypes: Wallis and Futuna Islands. MUSORSTOM 7 Stn DW 514, 14°13’S, 178°11’W, 349-355 m, 12.V.1992, 1 ♂ 2.9 mm, 1 ov. ♀ 3.3 mm (MNHN-IU-2011-5943, MNHN-IU-2011-5944). – Stn CP517, 14°13’S, 178°10’W, 223-235 m, 12.V.1992, 1 ♂ 3.3 mm (MNHN-IU-2011-5945), 2 ov. ♀ 3.3, 4.2 mm (MNHN- IU-2011-5946, MNHN-IU-2011-5947). Fiji Islands. MUSORSTOM 10 Stn CP 1389, 18°19’S, 178°05’E, 241-417 m, 19.VIII.1998, 1 ♂ 2.6 mm (MNHN-IU-2011-5939). BORDAU 1 Stn DW1454, 16°46’S, 179°59’E, 300-370 m, 4.III.1999, 1 ♂ 4.0 mm (MNHN-IU-2011-5940). Tonga. BORDAU 2 Stn CP1626, 23°20’S, 176°16’W, 220-249 m, 19.VI.2000, 1 ♂ 3.1 mm (MNHN-IU-2011-5942).
ETYMOLOGY„ From the Latin spinosior (more thorny), alluding to more spinose lateral margins of the carapace, a character to separate the species from the close relatives U. tridentatus (Henderson, 1885) and U. oxymerus Ahyong & Baba, 2004.
DISTRIBUTION„ Wallis and Futuna Islands (SW Pacific), Fiji Islands and Tonga; 220- 550 m.
SIZE„ Males, 2.6-4.0 mm; females, 3.3-4.2 mm; ovigerous females from 3.3 mm.
DESCRIPTION„ Small species. Carapace: Slightly broader than long (0.9 × as long as broad); greatest breadth 1.5-1.6 × distance between anterolateral spines. Dorsal surface feebly convex or nearly horizontal from anterior to posterior, smoothly sloping down to rostrum without any border, with or without weak depression between gastric and cardiac regions; with sparse or moderately dense, relatively long setae. Lateral margins convexly divergent posteriorly, with row of 12-18 spines: those on hepatic and anterior branchial margins small except for anterolateral spine, those on posterior branchial margin successively smaller posteriorly, all arranged in same level in profile; first (anterolateral) spine situated directly lateral to tiny lateral orbital spine, distinctly overreaching it; second much more distant from first than from third, last situated near posterior end. Rostrum straight and horizontal, narrow triangular, with interior angle 25-30°; dorsal surface concave; lateral margin with small subapical spine; length varying from more than half to less than half that of remaining carapace, breadth half carapace breadth at posterior carapace margin. Pterygostomian flap anteriorly angular, produced to sharp spine; surface with numerous small spines.
Sternum: Excavated sternum with anterior margin convex or broad subtriangular between bases of Mxp1, surface with ridge in midline. Sternal plastron slightly longer than broad, lateral extremities subparallel between sternites 4 and 7. Sternite 3 shallowly or moderately depressed; anterior margin shallowly excavated, with narrow (rarely broad), deep median notch without flanking spines. Sternite 4 having anterolateral margin feebly convex or nearly straight, less than twice as long as posterolateral margin, anteriorly angular. Anterolateral margins of sternite 5 subparallel, anteriorly rounded, about as long as posterolateral margin of sternite 4.
Abdomen: Smooth and sparsely setose. Somite 1 without transverse ridge. Somite 2 tergite 2.2-2.3 × broader than long; pleuron with lateral margin slightly concave, slightly or barely divergent posteriorly, anterior and posterior lateral termini rounded. Pleuron of somite 3 laterally blunt. Telson half as long as broad; posterior plate slightly or somewhat concave on posterior margin, length 1.1-1.5 × that of anterior plate.
Eye: Relatively broad (1.5 × longer than broad), slightly narrowed distally, somewhat overreaching midlength of rostrum. Cornea much more than half length of remaining eyestalk.
Antennule and antenna: Ultimate article of antennular peduncle 2.5-3.3 × longer than high. Antennal peduncle reaching subapical spine of rostrum. Article 2 with distinct lateral spine. Antennal scale distally sharp, reaching or somewhat overreaching distal end of article 5, breadth 1.2-1.3 × that of article 5. Distal 2 articles each ventrally armed with strong distomesial spine; article 5 1.5-1.9 × longer than article 4, breadth 0.6-0.7 × height of ultimate antennular article. Flagellum consisting of 9-11 segments, not reaching distal end of P1 merus.
Mxp: Mxp1 with bases distinctly separated. Mxp3 basis lacking denticles on mesial ridge. Ischium with small distal spine and tuft of long setae lateral to rounded distal end of flexor margin; crista dentata with 6-8 distally diminishing denticles, proximal denticles loosely arranged. Merus 1.7 × longer than ischium, broad relative to length, flattish on mesial face, with distolateral spine and 1 or 2 small spines distal to point distal third of cristate flexor margin. Carpus with 1 distolateral and 1 proximal extensor marginal spine.
P1: 4.3-5.4 × longer than carapace, subcylindrical (somewhat massive on palm in large males), covered with soft fine setae. Ischium dorsally with strong spine (rarely 2, distal larger), ventromesially with short subterminal spine and a few proximal tubercles. Blunt distomesial and distolateral spines on ventral surface of merus and carpus. Merus with 2-4 additional spines on proximal part of ventromesial surface, length 1.2-1.4 × that of carapace. Carpus 1.2-1.3 × longer than merus. Palm 3.0-3.7 × (males), 3.5-4.4 × (females) longer than broad, 0.95-1.1 × length of carpus. Fingers gently incurved distally and slightly crossing when closed, slightly gaping in both sexes; movable finger 0.4-0.5 × length of palm, opposable margin with obtuse subtriangular proximal process (very low in small specimens) fitting to longitudinal groove proximal to median process or between 2 eminences (in largest male) on opposable margin of fixed finger when closed.
P2-4: Meri moderately compressed mesio-laterally, successively shorter posteriorly (P3 merus 0.8-0.9 × length of P2 merus, P4 merus 0.9 × length of P3 merus), subequally broad on P2-4; dorsal margin with a few eminences or small spines on proximal half or several spines on entire length on P2 and often on P3, absent on P4; length-breadth ratio, 3.7-4.6 on P2, 3.2-3.9 on P3, 3.3-3.8 on P4; P2 merus 0.9 × length of carapace, 1.2 × length of P2 propodus; P3 merus 0.9 × length of P3 propodus; P4 merus 0.8-0.9 × length of P4 propodus. Carpi subequal on P3 and P4, slightly longer on P2 or subequal on P2-4; carpus-propodus length ratio, 0.3-0.4 on P2, 0.3 on P3 and P4. Propodi successively slightly longer posteriorly; flexor margin nearly straight or slightly concavely curving in lateral view, with pair of distal spines (preceded by 1 spine on P2 only in some paratypes). Dactyli 1.1-1.2 × longer than carpi and 0.4 × as long as propodi on P2-4; flexor margin nearly straight, with 6-7 spines loosely arranged and perpendicular to margin (excepting 1 or 2 proximal spines moderately inclined), ultimate spine slender, penultimate slightly larger than antepenultimate, both stronger than remainder.
Eggs. Eggs carried, 6-23; size, 0.75 mm × 0.80 mm.
REMARKS„ The combination of the following characters links the species to U. annae n. sp., U. oxymerus Ahyong & Baba, 2004 and U. tridentatus (Henderson, 1885): the rostrum bearing a subapical spine on each side, the sternal plastron with subparallel lateral extremities, the antenna bearing a strong spine on each of articles 4 and 5, the antennal scale overreaching article 5, Mxp3 with a small spine lateral to the rounded distal end of flexor margin, and the P2-4 dactyli bearing triangular spines perpendicular to the flexor margin. Uroptychus spinosior is readily distinguished from these congeners by having more numerous (12-18) spines along the entire lateral margin of the carapace, instead of at most 7 spines along the anterior three-quarters of the margin.
description: Published as part of Baba, Keiji, 2018, Chirostylidae of the Western and Central Pacific: Uroptychus and a new genus (Crustacea: Decapoda: Anomura), pp. 1-612 in Mémoires du Muséum national d'Histoire naturelle 212 on pages 491-495, DOI: 10.5281/zenodo.3760976