Uroptychus grandior, 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 : 225-229

Uroptychus grandior n. sp.

Figures 101 , 102

TYPE MATERIAL — Holotype: New Caledonia. LAGON Stn CP 1153, 18°58.14'S, 163°23.0’E, 330 m, 29.IX.1989, ♂ 2.4 mm ( MNHN-IU-2011-5929 ) . Paratypes: New Caledonia, Loyalty Islands. CALSUB PL11, 20°52,5’S, 167°03’E, 681- 140 m, 28.II.1989, 1 ♀ 1.6 mm (MNHN-IU-2011-5928) . New Caledonia, Norfolk Ridge. SMIB 4 Stn DW54, 23°41’S, 168°00’E, 230-235 m, 09.III.1989, 1 ov. ♀ 2.3 mm (MNHN-IU-2011-5925) . NORFOLK 1 Stn DW1657, 23°28’S, 167°52’E, 305-

332 m, 19.VI.2001, 1 ♂ 2.2 mm (MNHN-IU-2011-5927). – Stn CP1682, 24°43’S, 168°10’E, 331-379 m, 22.VI.2001, 1 ♂ 2.4 mm (MNHN-IU-2011-5926) .

ETYMOLOGY„ From the Latin grandior (larger), alluding to the unusually large distal second spine on the flexor margin of the P2-4 dactyli, one of the discriminating characters of the species.

DISTRIBUTION„ New Caledonia, Loyalty Islands and Norfolk Ridge; in 220- 379 m.

SIZE„ Males, 2.2-2.4 mm; females, 1.6-2.3 mm; ovigerous female, 2.3 mm.

DESCRIPTION„ Small species. Body and appendages with distally softened plumose setae.

Carapace: Slightly broader than long (0.8 × as long as broad); greatest breadth 1.5 × distance between anterolateral spines. Dorsal surface feebly convex or nearly straight horizontal from anterior to posterior, anteriorly smoothly continued on to rostrum; moderately setose, setae arising from short striae. Lateral margins convex, with 5 spines: first anterolateral, close to and directly lateral to lateral orbital spine, not overreaching that spine; second as large as first, remote from first and closer to third, occasionally preceded by eminence or 1 or 2 small spines; third to fifth situated on branchial margin; third larger than second and fourth; fifth much smaller than preceding two, followed by obsolescent spine or eminence and even additional small spine. Rostrum broad triangular, with interior angle of 32°, distally sharp, nearly straight horizontal, dorsal surface flattish; length slightly more than half that of carapace, breadth somewhat more than half carapace breadth measured at posterior carapace margin. Lateral orbital spine much smaller than anterolateral spine. Pterygostomian flap anteriorly angular, produced to small spine, surface smooth.

Sternum: Excavated sternum with convex anterior margin, bearing weak ridge in midline on surface (barely discernible in smallest specimen). Sternal plastron 1.2 × longer than broad, with subparallel lateral extremities, sternite 6 somewhat narrower than remainder. Sternite 3 shallowly depressed; broad V-shaped anterior margin with median sinus of broad U-shape, with no distinct flanking spine, laterally angular. Sternite 4 with anterolateral margin nearly straight, angular at anterior terminus; posterolateral margin relatively long, subequal to anterolateral margin in length. Anterolateral margin of sternite 5 somewhat convex, length 0.8 × that of posterolateral margin of sternite 4.

Abdomen: Smooth. Somite 1 without transverse ridge. Somite 2 tergite 2.1-2.3 × broader than long; pleuron posterolaterally blunt, lateral margin feebly concave and subparallel. Pleuron of somite 3 with rounded lateral margin. Telson about half as long as broad; posterior plate as long as anterior plate, posterior margin feebly convex.

Eye: Elongate, about twice as long as broad, distally narrowed, overreaching midlength of but barely reaching apex of rostrum. Cornea not dilated, less than half as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 2.5-3.3 × longer than high. Antennal peduncle reaching distal end of eyes. Article 2 with small distolateral spine. Antennal scale slightly less than twice as broad as article 5, distally sharp, extending far beyond article 5, falling short of rostral tip. Article 4 with well-developed distomesial spine. Article 5 with very small or distinct distomesial spine; length 1.5 × that of article 4, breadth 0.7 × height of antennular ultimate article. Flagellum consisting of 10-12 segments, slightly falling short of distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 with tufts of plumose setae on distal part of lateral margin of ischium, lateral face of merus and distal part of lateral face of carpus. Basis without distinct denticles on mesial ridge. Ischium with flexor margin distally rounded, crista dentata with small denticles diminishing distally. Merus 2.2 × longer than ischium, with distolateral spine, mesial face flattish, flexor margin sharply ridged with a few very small spines often obsolescent on distal third. Carpus unarmed.

P1: Relatively slender, subcylindrical, with tufts of relatively long setae, length 5.0-5.5 × that of carapace. Ischium dorsally bearing strong distal spine, ventrally unarmed. Merus 1.2-1.3 × longer than carapace, ventrally bearing distomesial and distolateral spines. Carpus 1.1-1.2 × longer than merus, ventrally with 2 distal spines. Palm 3.5-4.3 × longer than broad, 1.0-1.2 × longer than carpus. Fingers slightly curving laterally, distally incurved, crossing when closed, not gaping; movable finger 0.4 × length of palm, opposable margin with low, denticulate median process fitting to opposite narrow longitudinal groove on fixed finger when closed.

P2-4: Moderately compressed mesio-laterally. Meri relatively broad, successively slightly shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.9-1.0 × length of P3 merus), subequally broad on P2-4; length-breadth ratio, 3.1-3.3 on P2, 3.0-3.3 on P3, 2.8 on P4; dorsal crest with 4-5 short, acute spines along entire length on P2 and P3, a few obsolescent spines or eminences on proximal part on P4; ventrolateral margin with terminal spine distinct on P2, much smaller on P3, obsolescent on P4; P2 merus 0.7 length of carapace, about as long as P2 propodus; P3 merus 0.9 × length of P3 propodus; P4 merus 0.8 × length of P4 propodus. Carpi subequal, unarmed; carpus-propodus length ratio, 0.3-0.4 on P2 and P3, 0.3 on P4. Propodi subequal on P2 and P3 and longer on P4 or subequal on P3 and P4 and shorter on P2; flexor margin straight, with pair of distal spines only. Dactyli proportionately broad, about half as long as propodi; dactylus-carpus length ratio, 1.6 on P2, 1.5 on P3, 1.6 on P4; flexor margin nearly straight, bearing 6-7 spines, ultimate slender and curved, penultimate prominent, distinctly longer than remainder, about 3 × broader than antepenultimate, remaining spines slender, strongly inclined but not contiguous to one another, successively shorter toward base of article.

Eggs. Number of eggs carried, 5; size, 1.1 mm × 1.1 mm.

REMARKS — Uroptychus grandior strongly resembles U. belos Ahyong & Poore, 2004 in the spination of the carapace and P2-4 dactyli and in the elongate eyes. The two species each key out in a remotely different couplet (see under the key to species), due to the difference of length ratio of the anterolateral margin to the posterolateral margin of sternite 4. Uroptychus grandior can be distinguished from U. belos by the following differences: the eyes are distally narrowed instead of subequally broad proximally and distally; the dorsal crests of the P2-4 meri each bear a row of spines instead of being unarmed; the flexor marginal spines of the P2-4 dactyli are strongly oblique instead of gently inclined; and the antennal scale distinctly overreaches instead of terminating at most in the distal end of article 5.

Figures

FIGURE 101 Uroptychus grandior n. sp., holotype, male 2.4 mm (MNHN-IU-2011-5929). A, carapace and anterior part of abdomen, dorsal. B, same, lateral.C, anterior part of sternal plastron, with excavated sternum and basal parts of Mxp1. D, telson. E, left antenna, ventral.F, right Mxp3,setae omitted,ventral.G, left Mxp3,lateral.H, right P1, dorsal.I, same,proximal part,setae omitted,ventral. Scale bars:1 mm.

FIGURE 102 Uroptychus grandior n. sp., holotype, male 2.4 mm (MNHN-IU-2011-5929). A, left P2, lateral. B, same, distal part, setae omitted, lateral.C, left P3, setae omitted, lateral. D, left P4, setae omitted, lateral. E, same,distal part, setae omitted.Scale bars:1 mm.