Uroptychus duplex, 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 : 189-193

Uroptychus duplex n. sp.

Figures 82 , 83

TYPE MATERIAL — Holotype: New Caledonia, Norfolk Ridge. CHALCAL 2 Stn DW 73, 24°39.9’S, 168°38.1’E, 573 m, 2.X.1986, ov. ♀ 4.7 mm ( MNHN-IU-2011-5923 ) . Paratypes: New Caledonia, Norfolk Ridge. Station data as for the holotype, 1 ♂ 4.4 mm (MNHN-IU-2011-5924) . NORFOLK 2 Stn DW2091, 24°45’S, 168°06’E, 600-896 m, 29.X.2003, 1 ov. ♀ 5.1 mm (MNHN-IU-2011-5922) . New Caledonia, Isle of Pines. BIOCAL Stn CP52, 23°06’S, 167°47’E, 540-600 m, 31.VIII.1985, 1 ♂ 3.9 mm (MNHN-IU-2011-5921).

ETYMOLOGY„ The specific name is a noun in apposition from the Latin duplex (double) for the flexor marginal spines

of the P2-4 propodi which are arranged in double rows, not in a single row as in most of the other species.

DISTRIBUTION„ Isle of Pines and Norfolk Ridge; in 573 m. 320- 600 m.

DESCRIPTION„ Small species. Carapace: Much broader than long (0.6-0.7 × as long as broad); greatest breadth measured between last lateral spines situated at posterior quarter of lateral margin, 1.9-2.2 × distance between anterolateral spines. Dorsal surface well convex from anterior to posterior; anterior surface with sparse short setae, hepatic region with several scattered small spines. Lateral margins strongly convexly divergent posteriorly, with row of spines of irregular sizes as figured, first anterolateral, strong, overreaching smaller lateral orbital spine. Rostrum narrow triangular, with interior angle of 22-28°, slightly upcurved, length less than half that of remaining carapace, breadth about one-third carapace breadth measured at posterior carapace margin; dorsal surface concave. Lateral orbital spine distantly mesial to and very slightly anterior to anterolateral spine. Pterygostomian flap anteriorly angular, produced to distinct spine, surface with denticle-like very small spines on anterior half; height of posterior half 0.4 × that of anterior half.

Sternum: Excavated sternum subtriangular between bases of Mxp1, surface with low ridge in midline. Sternal plastron slightly less than twice as broad as long, depressed (in ventral view) on median parts of sternites 6 and 7; lateral extremities of sternites 4-7 convexly divergent posteriorly. Sternite 3 very short relative to breadth, not depressed; anterior margin broadly and shallowly excavated, transverse or very feebly concave on median third, without median notch. Sternite 4 with short lateral margin anteriorly rounded, posterolateral expansion very short, directed laterally, not anterolaterally. Anterolateral margin of sternite 5 strongly convex, much longer than posterolateral margin of sternite 4.

Abdomen: Smooth and glabrous, broad relative to length. Somite 1 without transverse ridge. Somite 2 tergite 2.6-2.8 × broader than long; pleuron anterolaterally rounded, posterolaterally angular, lateral margin feebly concavely divergent posteriorly. Pleura of somites 3 and 4 tapering to sharp point. Telson [0.2]-0.3 × as long as broad in female, 0.4 × in male; posterior plate 1.1-1.2 × that of anterior plate in males, 1.4-1.6 × in females, posterior margin broadly concave or feebly convex.

Eye: 1.5-1.6 × longer than broad, slightly broadened proximally, slightly overreaching midlength of rostrum. Cornea not inflated, more than half as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 3 × longer than high. Antennal peduncle distinctly overreaching cornea, falling short of apex of rostrum. Article 2 with sharp lateral spine. Antennal scale 2.0 × broader than article 5, slightly overreaching apex of rostrum, overreaching antennal peduncle by more than half length of article 5; lateral margin setiferous, bearing 1 or 2 small spines. Distal 2 articles unarmed; article 5 1.5 × longer than article 4, breadth 0.6 × height of antennular ultimate article. Flagellum consisting of 14-15 segments, falling short of distal end of P1 merus.

Mxp: Mxp1 with bases close to each other but not contiguous. Mxp3 laterally with fine plumose setae on ischium, merus and carpus. Basis without denticles on mesial ridge. Ischium with more than 30 very small denticles on crista dentata, flexor margin rounded distally. Merus 1.6-1.9 × longer than ischium, moderately compressed, distolaterally with distinct spine; flexor crest with 2 small spines distal to midlength. Carpus with small distolateral spine.

P1: 4.8-5.6 (females), 5.8-5.9 (males) × longer than carapace; with soft setae sparingly on fingers and along mesial margin. Ischium with basally broad, depressed, triangular dorsal process, ventromesially with row of 4 or 5 tubercle-like small spines on proximal two-thirds, without subterminal spine. Merus mesially with obsolescent denticles on proximal portion, length slightly more than that of carapace. Carpus 1.4-1.5 (males), 1.3-1.5 (females) × longer than merus, unarmed. Palm 3.7-3.8 (males), 3.8-4.2 (females) × longer than broad, 1.0-1.2 (females), 1.0-1.3 (males) × longer than carpus, more or less depressed. Fingers distally incurved and weakly crossing; movable finger 0.4 (females), 0.3 (males) × as long as palm, opposable margin with low subtriangular proximal process fitting into longitudinal groove proximal to median eminence on opposing fixed finger when closed.

P2-4: Sparsely setose, relatively broad, and unarmed except for distal 2 articles. Meri broad relative to length, largest on P3, smallest on P4, P2 merus 0.9 × P3 merus in length and breadth, P4 merus 0.5-0.6 × P3 merus in length, 0.8 × in breadth; P2 merus as long as or slightly shorter than carapace, 1.2 × length of P2 propodus; P3 merus 1.0-1.1 × length of P3 propodus; P4 merus 0.8 × length of P4 propodus; length-breadth ratio, 2.9-3.3 on P2, 2.8-3.4 on P3, 2.5 on P4. Carpi longest on P3, shortest on P4 (P3 carpus 1.1 × longer than P2 carpus, P4 carpus 0.7 × length of P3 carpus), carpus-propodus length ratio, 0.6 on P2-4. Propodi longer on P3 than on P2 and P4; extensor margin nearly straight; flexor margin inflated around point one-third from distal end, subprehensile with dactylus on distal third of length, bearing double rows of slender mesial spines, terminal spines paired. Dactyli distinctly shorter than carpi (dactylus-carpus length ratio, 0.7 on P2 and P3, 0.9 on P4); flexor margin moderately curved at proximal quarter, with row of 12 or 13 slightly inclined, subtriangular spines, ultimate more slender than penultimate, remaining spines gradually diminishing toward base of article.

Eggs. Number of eggs carried, up to 16; size, 1.58 mm × 1.38 mm.

REMARKS — Uroptychus duplex is very similar to U. macrolepis n. sp. and U. zigzag n. sp. in the spination of the carapace lateral margin, in having the pterygostomian flap very low on the posterior half, in the shape of the antenna, in having the P3 merus distinctly longer than the P2 merus, and in the spination of the P2-4 dactyli. The relationships are discussed under the remarks of these congeners (see below).

Figures

FIGURE 82 Uroptychus duplex n.sp.,holotype,ovigerous female 4.7 mm(MNHN-IU-2011-5923).A, carapace and anteriorpart of abdomen, proximal articles 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, setae omitted,ventral.G, same, lateral.H, right P1, proximal part, setae omitted, ventral.I, same,dorsal. Scale bars: 1 mm.

FIGURE 83 Uroptychus duplex n. sp.,holotype,ovigerous female 4.7 mm (MNHN-IU-2011-5923). A, right P2,lateral. B, same,distal part,setae omitted, lateral.C, right P3, lateral. D, same, distal part, lateral. E, right P4,lateral.F, same,distal part,lateral.Scale bars:1 mm.