Uroptychus denticulifer, 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 : 163-166

Uroptychus denticulifer n. sp.

Figures 67 , 68

TYPE MATERIAL — Holotype: Solomon Islands. SALOMON 1 Stn DW1854, 9°46.4’S, 160°52.9’E, 229-260 m, 7.X.2001, ov. ♀ 2.5 mm ( MNHN-IU-2014-16380 ). Paratype: Vanuatu. MUSORSTOM 8 Stn DW1060, 16°14’S, 167°21’E, 394- 375 m, 2.X.1994, 1 ♂ 2.3 mm (MNHN-IU-2014-16381) .

ETYMOLOGY„ From the Latin denticulus (dim. of dens, tooth) and fer (to bear), referring to the denticles covering the body.

DISTRIBUTION„ Solomon Islands and Vanuatu; 229- 397 m.

DESCRIPTION„ Small species. Carapace: 0.8-0.9 × as long as broad; greatest breadth 1.7 × distance between anterolateral spines. Dorsal surface covered with denticles, inflated on lateral gastric, cardiac and lateral branchial regions, with deep groove separating gastric and cardiac regions; anterolateral spine small, not reaching tip of lateral orbital spine, followed by convex lateral margin leading to ordinary end of cervical groove, then followed by inflation on anterior branchial region and convexly divergent posterior branchial margin. Rostrum subtriangular, with interior angle of 22°, distally roundish, not tapering; dorsal surface concave; length about half that of remaining carapace. Lateral orbital spine larger than or subequal to anterolateral spine, situated directly mesial to (at same level as) and more or less close to that spine. Pterygostomian flap covered with denticles, anteriorly roundish, with small spine.

Sternum: Excavated sternum with convex anterior margin, moderately ridged in midline. Sternal plastron slightly longer than broad, sternite 4 as broad as sternite 5, slightly broader than sternite 6, sternite 7 broader than sternite 4. Sternite 3 shallowly depressed, weakly concave on anterior margin bearing narrow, deep median sinus without flanking spine. Sternite 4 with anterolateral margin rounded at anterior end bearing a few obsolescent denticles; posterolateral margin longer than anterolateral margin. Anterolateral margin of sternite 5 strongly convex and posteriorly divergent, about half as long as posterolateral margin of sternite 4.

Abdomen: Somites long relative to breadth, bearing denticles on somites 1 and 2 (and on anterior part of somite 3 in holotype), smooth elsewhere. Somite 1 convex from anterior to posterior. Somite 2 tergite 1.9-2.0 × broader than long; pleural margin feebly concave and slightly divergent posteriorly, posterolateral end rounded. Pleuron of somite 3 laterally rounded. Telson 0.4-0.5 × as long as broad; posterior plate slightly shorter than anterior plate, posterior margin slightly concave.

Eye: Broad relative to length (length 1.4-1.5 × breadth), slightly overreaching midlength of rostrum; lateral and mesial margins slightly or distinctly convex, dorsal surface with or without sparse denticles. Cornea not inflated, length less than half that of remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 2.0 × longer than high. Antennal peduncle reaching apex of rostrum. Article 2 fused with antennal scale, without lateral spine. Antennal scale slightly overreaching distal end of article 4, with small blunt spines along lateral margin. Article 4 ventrally with a few denticles on terminal margin at juncture with article 5. Article 5 1.6 × length of article 4, unarmed; breadth 0.6-0.7 × height of antennular ultimate article. Flagellum of 6 segments about as long as antennal peduncle, not reaching distal end of P1 merus.

Mxp: Mxp1 with bases moderately separated. Mxp3 sparsely setose on lateral surface. Basis with obsolescent denticles on mesial ridge. Ischium with distally rounded flexor margin; crista dentata with obsolescent denticles. Merus 2.8 × longer than ischium, not cristate but roundly ridged along flexor margin, with short distolateral process distally bearing a few denticles; with scattered small spines or denticles on lateral surface and a few denticles on distal half of flexor margin. Carpus also with scattered denticles dorsally and laterally.

P1: 6.9 × longer than carapace, slender, sparsely with soft setae. Ischium with truncate, broad, depressed dorsal process, ventromesially feebly denticulate, lacking subterminal spine. Merus 1.4-1.5 × longer than carapace, mesially with small, blunt spines on proximal half, dorsally and ventrally with denticulate ridges supporting setae. Carpus 1.3-1.5 × longer than merus, with obsolescent denticulate ridges, unarmed. Palm 6.7 × longer than broad, 0.9 × length of carpus. Fingers somewhat incurved distally, not spooned along opposable margins; opposable margin with 2 low processes on movable finger, low median eminence on fixed finger; movable finger 0.3 × length of palm.

P2-4: Relatively thick mesio-laterally, sparsely setose, setae relatively long. Meri successively slightly broader posteriorly or subequally broad, successively shorter posteriorly (P3 merus 0.8 × length of P2 merus, P4 merus 0.9 × length of P3 merus); length 3.8-4.0 × breadth on P2, 3.1-3.3 × on P3, 2.8-3.0 × on P4; P2 merus 0.7-0.8 × length of carapace, as long as P2 propodus; P3 merus 0.8 × length of P3 propodus; P4 merus 0.70-0.75 × length of P4 propodus; dorsal margin with row of short spines, lacking spine at distal end; lateral surface with short denticulate ridges supporting setae. Carpi subequal, about one-third length of propodi (0.30-0.33 on P2, 0.28-0.33 on P3, 0.30-0.31 on P4); lateral surface with a few denticulate ridges supporting setae paralleling extensor margin. Propodi subequal in length on P2 and P3 and longer on P4 or shortest on P2 and subequal on P3 and P4; flexor margin slightly concave in lateral view, with pair of terminal spines only. Dactyli about 1.5 × length of carpi on P2-4 (1.4 × on P2, 1.6 × on P3, 1.5 × on P4), about half as long as propodi on P2-4; flexor margin slightly curving, with prominently broad, long penultimate spine preceded proximally by 5 or 6 loosely arranged, obliquely directed, slender spines; ultimate spine much more slender than antepenultimate.

Eggs. Five eggs carried; size, 0.76 m × 0.88 mm - 0.77 mm × 0.92 mm.

REMARKS — The new species strongly resembles U. kaitara Schnabel, 2009 from the Kermadec Ridge in having the body covered with denticles (on the carapace, pterygostomian flap and at least anterior two somites of the abdomen), in having the anterolateral spine of the carapace small and subequal to or smaller than the lateral orbital spine, and in the shape of sternite, especially the posterolateral margin about as long as or longer than the anterolateral spine. It is differentiated from that species by the following: the antennal scale is fused instead of articulated with the antennal article 2; the antennal article 5 is 1.6 times longer than instead of being subequal to article 4; and the P2-4 dactyli bear flexor marginal spines obliquely directed instead of perpendicular to the margin.

Figures

FIGURE 67 Uroptychus denticulifer n. sp., holotype, ovigerous female 2.5 mm (MNHN-IU-2014-16380). 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, same,lateral. H, right P1, ischium,lateral. I, same,proximal part,ventral. J, same,dorsal.Scale bars: 1 mm.

FIGURE 68 Uroptychus denticulifer n. sp., holotype, ovigerous female 2.5 mm (MNHN-IU-2014-16380). 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.