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

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Uroptychus grandior

n. sp.

Uroptychus grandior n. sp.

Figures 101 View FIGURE 101 , 102 View FIGURE 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- View Figure View Figure

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 P 2-4 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 P 1 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.

P 1: 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.

P 2-4: Moderately compressed mesio-laterally. Meri relatively broad, successively slightly shorter posteriorly ( P 3 merus 0.9 × length of P 2 merus, P 4 merus 0.9-1.0 × length of P 3 merus), subequally broad on P 2-4; length-breadth ratio, 3.1-3.3 on P 2, 3.0-3.3 on P 3, 2.8 on P 4; dorsal crest with 4-5 short, acute spines along entire length on P 2 and P 3, a few obsolescent spines or eminences on proximal part on P 4; ventrolateral margin with terminal spine distinct on P 2, much smaller on P 3, obsolescent on P 4; P 2 merus 0.7 length of carapace, about as long as P 2 propodus; P 3 merus 0.9 × length of P 3 propodus; P 4 merus 0.8 × length of P 4 propodus. Carpi subequal, unarmed; carpus-propodus length ratio, 0.3-0.4 on P 2 and P 3, 0.3 on P 4. Propodi subequal on P 2 and P 3 and longer on P 4 or subequal on P 3 and P 4 and shorter on P 2; 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 P 2, 1.5 on P 3, 1.6 on P 4; 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 P 2-4 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 P 2-4 meri each bear a row of spines instead of being unarmed; the flexor marginal spines of the P 2-4 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.