Uroptychus macrolepis, 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 : 290-294

Uroptychus macrolepis n. sp.

Figures 135 , 136

TYPE MATERIAL — Holotype: New Caledonia. MUSORSTOM 4 Stn CP 213, 22°51.30’S, 167°12.0’E, 405-430 m, on corals of Antipatharia (Hexacorallia), 28.IX.1985, ♂ 3.1 mm ( MNHN-IU-2013-8517 ) . Paratypes: MUSORSTOM 4, station data as for the holotype, 1 ov. ♀ 3.2 mm (MNHN-IU-2014-16715) . New Caledonia, Norfolk Ridge. BATHUS 3 Stn DW817, 23°42’S, 168°16’E, 405-410 m, 28.XI.1993, 1 ♂ 3.2 mm (MNHN-IU-2014-16716) . NORFOLK 2 Stn CP2048, CP2048, 23°43.82S, 168°16.24’E, 380-389 m, 24.X.2003, 1 ♂ 2.6 mm (MNHN-IU-2014-16717).

ETYMOLOGY„ From the Greek macros (long) and lepis (scale), alluding a long antennal scale displayed by the species.

DISTRIBUTION„ New Caledonia and Norfolk Ridge; 380- 430 m.

SIZE„ Males, 2.6-3.2 mm; ovigerous female, 3.2 mm.

DESCRIPTION„ Small species. Carapace: Strongly broadened posteriorly, 1.3-1.4 × broader than long (0.7 × as long as broad); greatest breadth 1.8-1.9 × distance between anterolateral spines. Dorsal surface moderately convex from anterior to posterior, smooth, with very sparse soft setae, lacking distinct depression. Lateral margins divided into anterior and posterior parts by concavity or constriction at point one-third from anterior end or directly anterior to posterior bran- chial margin, anterior part more or less convexly divergent, with 4 spines; first spine anterolateral, well developed, reaching or slightly overreaching lateral orbital spine; second and third somewhat ventral in position (third absent in 2 specimens); fourth as large as first; posterior part (posterior branchial margin) strongly convex, with 5 relatively small, posteriorly diminishing spines, anteriormost of these remotely separated from preceding spine, last spine situated at posterior third of posterior branchial margin. Rostrum narrowly triangular, with interior angle of about 20°, deflected ventrally, dorsally concave; length about half that of remaining carapace, breadth one-third carapace breadth at posterior carapace margin. Lateral orbital spine slightly smaller than or subequal to anterolateral spine, situated very slightly anterior to but well separated from that spine. Pterygostomian flap anteriorly angular, produced to acute spine followed by 1 or 2 distinct spines anterior to anterior linea anomurica; no spines on surface; height of posterior half 0.3 × that of anterior half.

Sternum: Excavated sternum with broad subtriangular anterior margin ending in blunt tip, bearing weak ridge in midline. Sternal plastron much broader than long (0.6 × as long as broad), lateral extremities convexly divergent posteriorly, sternite 6 broadest. Sternite 3 very shallowly depressed, anterior margin shallowly or moderately concave, with obsolescent or small median notch, lacking submedian spines; anterolateral end sharply angular. Sternite 4 with convex anterolateral margin not produced anteriorly, posterolateral margin very short. Anterolateral margin of sternite 5 strongly convex, about twice as long as posterolateral margin of sternite 4.

Abdomen: Tergites smooth, polished, sparsely with short setae, each somite short relative to width. Somite 1 without transverse ridge. Somite 2 tergite 3.2-3.3 × broader than long; pleuron slightly concavely divergent posteriorly, blunt at end. Pleuron of somite 3 with blunt lateral end. Telson slightly less than half as long as broad; posterior plate feebly concave or feebly convex on posterior margin, length 1.3-1.8 × that of anterior plate.

Eye: Elongate (2.6-3.2 × longer than broad), reaching at most distal third of rostrum, narrowed distally (in smallest male, eyes 2.2 × longer than broad, distally not narrowed). Cornea distinctly less than half length of remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 2.8-3.0 × longer than high. Antennal peduncle not overreaching cornea. Article 2 with acute, short lateral spine. Antennal scale overreaching distal end of peduncle by half length of article 5, reaching or slightly overreaching rostral tip, breadth 1.5 × that of article 5. Distal 2 articles unarmed; article 5 1.3-1.5 × longer than article 4, breadth three-fifths to four-fifths height of ultimate article of antennule. Flagellum of 10-12 segments reaching or falling short of distal end of P1 merus.

Mxp: Mxp1 with bases close to each other. Mxp3 with relatively short setae. Basis with a few obsolescent denticles on mesial ridge. Ischium with distally diminishing small denticles on crista dentata, flexor margin distally rounded. Merus 2 × as long as ischium, with prominent distolateral spine and 2 smaller spines distal to point two-thirds of sharply ridged flexor margin. Carpus with distinct distolateral spine.

P1: 5.3-5.6 × longer than carapace, thickly covered with fine, plumose, long setae. Ischium dorsally with strong spine, ventromesially with 3-6 small spines, subterminal spine absent. Merus 1.0-1.2 × length of carapace, with 3-5 mesial, 1 ventral distomesial, 1 very reduced ventral distolateral spine. Carpus 1.2-1.3 × longer than merus, mesially with 2 small blunt spines (distodorsal and distoventral). Palm 2.7-3.3 × longer than broad, 1.3 × longer than carpus, unarmed. Fingers not gaping in both sexes, strongly incurved distally, crossing when closed; movable finger slightly shorter than fixed finger, length 0.4-0.5 × that of palm, opposable margin with low proximal process; fixed finger directed feebly laterally, opposable margin with median eminence.

P2 -4: Unarmed except for 2 distal articles, with long fine plumose setae particularly thick along dorsal or extensor margins. Meri relatively broad, distally somewhat narrowed; length-breadth ratio, 3.5-3.8 on P2, 3.3-3.5 on P3, 2.7-3.0 on P4; dorsal margin with or without obsolescent eminences; P2 merus as long as or slightly shorter than (0.9 × length of) carapace, slightly longer than P2 propodus; P3 merus slightly broader and slightly longer than P2 merus, 1.1 × length of P3 propodus; P4 merus very slightly narrower than or as broad as P2 merus, 0.7-0.8 × length of P3 merus, 0.8-0.9 × length of P4 propodus. Carpi about as long as dactyli on P2-4; P3 carpus as long as P2 carpus, P4 carpus 0.9-1.0 × length of P2 carpus, 0.8-1.0 × length of P3 carpus; carpus-propodus length ratio, 0.5 on P2 and P3, 0.4-0.5 on P4. Propodi subequal on P2-4 or slightly longer on P2 or P3 (not consistent), relatively broad; flexor margin convex (broadest portion measured at midlength), ending in pair of movable spines preceded by 5-7 slender spines in zigzag arrangement on distal half, distalmost of these unpaired spines somewhat more remote from distal pair than from their distal second. Dactyli relatively stout, strongly curved at proximal third; length 0.4-0.5 × that of propodus on P2-4; flexor margin with 11-13 short, triangular, obliquely directed spines, ultimate slender, penultimate broader than antepenultimate, antepenultimate broader than ultimate, ultimate and penultimate nearly contiguous at base.

Eggs. Eggs carried 4 in number, measuring 1.10 mm in diameter.

REMARKS — The combination of the following characters links the species to U. duplex n. sp. and U. zigzag n. sp.: the posteriorly broadened carapace bearing lateral spines, the antennal scale overreaching the antennal article 5, the P2 merus subequal to or slightly shorter than the P3 merus, and the P2-4 propodi inflated on the distal part of flexor margin.

Uroptychus duplex and U. macrolepis share a well-depressed cephalothorax, the posterior half in particular, with the pterygostomian flap much lower in the posterior half than in the anterior half. Uroptychus duplex is distinguished from U. macrolepis by sternite 3 that has the anterior margin transverse along the median third length, not concavely excavated; the sternal plastron is strongly broadened posteriorly and broadest on sternite 7; and the anterolateral spine of the carapace is much larger than instead of slightly larger or subequal to the lateral orbital spine.

The relationships with U. zigzag are discussed under the remarks of that species (see below).

Figures

FIGURE 135 Uroptychus macrolepis n. sp.,holotype, male 3.1 mm (MNHN-IU-2013-8517).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, antenna and anterior part of pterygostomian flap,ventral.F, left Mxp3,setae omitted,ventral.G, same,lateral.H, right P1, dorsal.I, same,proximal part,setae omitted, ventral.Scale bars:1 mm.

FIGURE 136 Uroptychus macrolepis n. sp., holotype, male 3.1 mm (MNHN-IU-2013-8517).A, left 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.