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

description: Uroptychus nebulosus n. sp.
Figures 160, 161, 305I
Uroptychus sibogae — Poore et al. 2011: 330, pl. 8, fig. A (not U. sibogae Van Dam, 1933).
TYPE MATERIAL — Holotype: Tonga. BORDAU 2 Stn CH 1621, 24°19’S, 176°23’W, 570-573 m, 18.VI.2000, ♂ 9.5 mm (MNHN-IU-2014-16804). Paratypes: Tonga. BORDAU 2, station data as for the holotype, 1 ♂ 8.7 mm, 1 ov. ♀ 9.0 mm (MNHN-IU-2014-16805). – Stn CP1620, 24°18’S, 176°20’W, 572 m, 18.VI.2000, 1 ♂ 9.6 mm, 1 ov. ♀ 11.1 mm (MNHN- IU-2014-16806). Solomon Islands. SALOMON 1 Stn DW1788, 09°19’S, 160°15’E, 341-343 m, 30.IX.2001, 2 ♂ 4.8, 5.1 mm (MNHN-IU-2014-16807). SALOMON 2 Stn CP2262, 7°56.4’S, 156°51.2’E, 460-487 m, 3.XI.2004, 1 ♂ 4.9 mm (MNHN-IU-2014-16808). – Stn CP2263, 7°54.8’S, 156°51.3’E, 485-520 m, 3.XI.2004, 1 ♂ 7.2 mm, 1 ov. ♀ 6.8 mm (MNHN-IU-2014-16809). Vanuatu. SANTO Stn AT09, 15°42’S, 167°01’E, 481 m, 17.IX.2006, 2 ♂ 6.6, 7.6 mm (MNHN- IU-2014-16810). – Stn AT10, 15°41.1’S, 167°00.5’E, 509-559 m, 17.IX.2006, 1 ♂ 6.5 mm (MNHN-IU-2014-16811). – Stn AT73, 15°40.8’S, 167°00.5’E, 514-636 m, 07.X.2006, 1 ♂ 8.1 mm (MNHN-IU-2014-16812), 3 ♂ 5.6-7.9 mm, 1 ov. ♀ 6.0 mm, 1 ♀ 5.7 mm (MNHN-IU-2014-16813). New Caledonia, Hunter and Matthew Islands. VOLSMAR Stn DW05, 22°26’S, 171°46’E, 620-700 m, 01.VI.1989, 4 ♂ 4.4-6.2 mm, 1 ov. ♀ 5.7 mm (MNHN-IU-2014-16814). New Caledonia. MUSORSTOM 4 Stn CP216, 22°59.5’S, 167°22.0’E, 490-515 m, with Chrysogorgiidae gen. sp. (Calcaxonia), 29.IX.1985, 1 ♂ 5.7 mm (MNHN-IU-2014-16815). French Polynesia, Austral Islands. BENTHAUS Stn DW2001, 22°26.6’S, 151°20.1’W, 200-550 m, 23.XI.2002, 1 ov. ♀ 6.1 mm (MNHN-IU-2014-16816).
ETYMOLOGY„ From the Latin nebulosus (indefinite, obscure), alluding to the systematic status of this species which is very similar to U. sibogae Van Dam, 1933 and U. longicarpus n. sp., but the species is distinctive in subtle detail.
DISTRIBUTION„ Solomon Islands, Vanuatu, Hunter-Matthew Islands, New Caledonia, Tonga and French Polynesia; 200- 700 m.
SIZE„ Males, 4.4-9.6 mm; females, 5.7-11.1 mm; ovigerous females from 5.7 mm.
DESCRIPTION„ Medium-sized to large species. Carapace: As long as or slightly longer than broad; greatest breadth 1.5 × distance between anterolateral spines. Dorsal surface smooth, with very fine, short setae discernible under high magnification, slightly convex from anterior to posterior, feebly concave between gastric and cardiac regions. Lateral margins slightly convex and slightly divergent posteriorly; anterolateral spine small, located posterior to level of smaller lateral orbital spine, and never overreaching its tip; another spine located at anterior end of branchial region, followed by row of feebly denticulate short ridges; ridged along posterior sixth of length. Rostrum elongate, sharp triangular, with interior angle 27-35°; dorsal surface moderately concave; length 0.4-0.5 × that of remaining carapace, breadth slightly more than half carapace breadth at posterior carapace margin. Pterygostomian flap anteriorly angular, produced to very small spine, surface smooth.
Sternum: Excavated sternum with sharp anterior spine between bases of Mxp1, surface with spine in center. Sternal plastron as long as broad or slightly shorter; lateral extremities divergent posteriorly. Sternite 3 strongly depressed, anterior margin strongly excavated, with 2 well-developed submedian spines nearly contiguous or separated by narrow notch, anterolateral angle rounded or angular. Sternite 4 long relative to breadth, anterolaterally sharp angular; anterolateral margin smoothly straight, length 2.6-3.2 × that of posterolateral margin. Anterolateral margin of sternite 5 anteriorly rounded, 1.5-1.6 × longer than posterolateral margin of sternite 4.
Abdomen: Smooth, with very fine setae. Somite 1 antero-posteriorly convex, not ridged. Somite 2 tergite 2.2-2.4 × broader than long; pleuron with anterolaterally rounded, posterolaterally angular, lateral margin concavely strongly divergent. Pleuron of somite 3 with angular lateral terminus. Telson 0.6-0.7 × as long as broad; posterior plate 1.5-2.1 × longer than anterior plate, emarginate on posterior margin.
Eye: 1.6-2.0 × longer than broad, overreaching midlength of rostrum but not reaching rostral tip; lateral and mesial margins subparallel. Cornea slightly inflated, more than half as long as remaining eyestalk.
Antennule and antenna: Ultimate article of antennule 2.0-2.5 × longer than high. Antennal peduncle not reaching distal end of cornea. Article 2 with very small or obsolescent lateral spine. Antennal scale slightly falling short of or nearly reaching distal end of article 5, 1.6 × broader than article 5. Article 4 unarmed. Article 5 with small distomesial spine, length 2.5-2.6 × that of article 4, breadth 0.4 height of ultimate antennular article. Flagellum of 22-24 segments slightly falling short of distal end of P1 merus.
Mxp: Mxp1 with bases close to each other. Mxp3 basis with 3 or 4 denticles on mesial ridge, distalmost consistent, others often obsolescent. Ischium with 20-25 denticles on crista dentata, flexor margin distally not rounded. Merus about twice as long as ischium, unarmed, moderately ridged along flexor margin. Carpus unarmed.
P1: 4.7-5.0 × longer than carapace, massive, setose on fingers and distal part of palm, ventrally granulose except for palm and fingers; triangular dorsal spine on ischium, unarmed elsewhere. Merus 1.1-1.2 × longer than carapace. Carpus 1.1-1.3 × longer than merus. Palm 2.1-2.6 × (males), 2.5-2.7 × (females) longer than broad, 0.9-1.0 × longer than carpus. Fingers gaping in males, not gaping in females and small males, distally incurved, crossing when closed; movable finger 0.6-0.7 × length of palm, opposable margin with medially incised proximal process.
P2-4: Broad relative to length, dactyli narrow. Meri moderately compressed mesio-laterally, sparingly with long setae, successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.8-0.9 × length of P3 merus); successively narrower posteriorly (P4 merus 0.9 × breadth of P2 merus, 0.8-0.9 × breadth of P3 merus); length-breadth ratio, 3.5-3.7 on P2, 3.3-3.9 on P3, 3.6-4.0 on P4; P2 merus 0.8 × length of carapace, 1.2-1.4 × length of P2 propodus; P3 merus subequal to length of P3 propodus; P4 merus 0.9 × length of P4 propodus. Carpi successively shorter posteriorly (P3 carpus 0.9 × length of P2 carpus, P4 carpus 0.9 × length of P3 carpus); carpus-dactylus length ratio, 1.3-1.7 on P2, 1.2-1.4 on P3, 1.0-1.3 on P4; carpus-propodus length ratio, 0.6 on P2, 0.5 on P3, 0.4-0.5 on P4. Propodi subequal in length on P3 and P4 (shortest on P2) or on P2 and P3 (longest on P4); flexor margin straight, terminating in pair of spines preceded by 9-11 spines on P2, 8-9 spines on P3, 6-8 spines on P4. Dactyli subequal, 0.6-0.8 × length of carpi on P2, 0.7-0. 8 × on P3, 0.8-1.0 × on P4, 0.4 × length of propodi on P2-4; flexor margin strongly curving at proximal quarter, with 9-10 subtriangular, somewhat inclined, proximally decreasing spines on P2, 10-11 spines on P3, 10-12 spines on P4, ultimate largest, penultimate and antepenultimate subequal.
Eggs. Number of eggs carried, about 60; size, 1.28 mm × 1.36 mm - 1.37 mm × 1.40 mm.
Color. Pale orange overall, posterior half of carapace translucent white (male 8.1 mm, MNHN-IU-2014-16812; male 6.5 mm, MNHN-IU-2014-16811). The color illustration given under U. sibogae by Poore et al. (2011) is from one of the photos (MNHN-IU-2014-16811) available to me.
REMARKS — The species is very closely related to U. sibogae Van Dam, 1933 (see below) and U. longicarpus n. sp. in nearly all aspects. Uroptychus nebulosus is distinguished from U. sibogae by subtle morphological differences: the P2 merus is longer and broader than instead of subequal to or slightly narrower than P3 merus; the P2-4 meri are broader relative to length (the length-breadth ratio being 3.7-3.9, 3.4-4.1, 3.6-3.8 versus 5.0-5.6, 5.0-5.3, 4.2-4.6 on P2, P3, P4 respectively; the P2 merus is much shorter than instead of subequal to the carapace (0.8 versus 1.0); and the cornea is not so well inflated as in U. sibogae. Uroptychus longicarpus n. sp. is unique in the genus in having the P4 carpus distinctly longer than the P3 carpus.
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 337-340, DOI: 10.5281/zenodo.3760976