Uroptychus laurentae, 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 : 266-270

Uroptychus laurentae n. sp.

Figures 123 , 124

TYPE MATERIAL — Holotype: New Caledonia, Chesterfield Islands . MUSORSTOM 5 Stn DW 272, 24°41’S, 159°43’E, 500-540 m, 09.X.1986, 1 ♂ 2.9 mm ( MNHN-IU-2014-16617 ).

ETYMOLOGY„ The name is dedicated to the late Michéle de Saint Laurent who had shared the interest with me in squat lobsters.

DISTRIBUTION„ Chesterfield Islands; 500- 540 m.

DESCRIPTION„ Small species. Carapace: Slightly broader than long (0.9 × as long as broad); greatest breadth 1.5 × distance between anterolateral spines. Dorsal surface with scattered setae, moderately convex from side to side, nearly horizontal on gastric region, somewhat convex behind it, with shallow groove bordering gastric and cardiac regions. Lateral margins convex medially, with row of 7 small spines; first spine anterolateral, not reaching tip of lateral orbital spine, followed by small dorsal spine directly behind it; second spine rather remote from first, situated at anterior end of branchial margin, preceded by row of tubercle-like denticles placed somewhat dorsomesially; 5 other spines along posterior branchial region. Rostrum broad triangular, with interior angle of 20°, straight and horizontal; dorsal surface moderately concave; length 0.7 × postorbital carapace length, breadth somewhat more than half carapace breadth at posterior carapace margin. Lateral orbital spine slightly smaller than anterolateral spine, situated directly mesial and very slightly anterior to level of that spine. Pterygostomian flap with tubercles on anterior surface, anterior margin sharp angular and spiniform; dorsal margin anterior to linea anomurica with a few tubercle-like spinules.

Sternum: Excavated sternum with anterior margin nearly transverse, surface ridged in midline. Sternal plastron 1.2 × longer than broad, broadest on sternite 4, lateral extremities subparallel between sternites 5-7. Sternite 3 shallowly depressed, anterior margin shallowly excavated, with small V-shaped median notch lacking flanking spine. Sternite 4 having anterolateral margin nearly smooth, slightly convex, anteriorly blunt; posterolateral margin distinctly longer than anterolateral margin. Anterolateral margins of sternite 5 subparallel, anteriorly rounded, about half length of posterolateral margin of sterntie 4.

Abdomen: Smooth, sparsely setose. Somite 1 without transverse ridge. Somite 2 tergite 2.1 × broader than long; pleuron posterolaterally rounded, lateral margin shallowly concave and weakly divergent posteriorly. Pleuron of somite 3 posterolaterally blunt. Telson about half as long as broad, posterior plate 1.3 × longer than anterior plate, posterior margin feebly concave.

Eye: Relatively short (1.5 × longer than broad), slightly overreaching midlength of rostrum; lateral and mesial margins subparallel. Cornea not dilated, length slightly less than that of remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 3.5 × longer than high. Antennal peduncle overreaching cornea by half length of article 5. Article 2 with distinct distolateral spine. Antennal scale slightly broader than article 5, ending in blunt tip, slightly falling short of midlength of article 5; lateral margin with small proximal spine on left appendage. Distal 2 articles unarmed; article 5 1.2 × longer than article 4, breadth slightly smaller than height of ultimate antennular article. Flagellum consisting of 10-11 segments, not reaching distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 basis with proximally rounded mesial ridge bearing no distinct denticle. Ischium with obsolescent denticles on crista dentata; flexor margin not rounded distally. Merus 2.6 × length of ischium, distolateral spine obsolescent; flexor margin not sharply cristate but moderately ridged and unarmed. Carpus spineless.

P1: Unequal in size, left smaller, presumably regenerated. Right P1 5.8 × longer than carapace. All articles sparsely setose as figured. Ischium dorsally with depressed process, ventrally with a few denticles on proximal mesial margin, without distinct subterminal spine. Merus and carpus subcylindrical and unarmed. Merus 1.3 × longer than carapace. Carpus 1.3 × longer than merus. Palm 3.5 × longer than broad, slightly longer than carpus. Fingers slightly gaping, distally somewhat incurved, ending in blunt short spine, not spooned; movable finger less than half length of palm, opposable margin with low median process fitting to narrow longitudinal groove on opposite fixed finger when closed; fixed finger directed somewhat laterally, opposable margin with low prominence slightly distal to opposite median process of movable finger.

P2-4: Sparsely setose. Meri broad relative to length, length-breadth ratio, 3.1 on P2, 2.8 on P3, 2.6 on P4, successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.9 × length of P3 merus), equally broad on P2-4; dorsal margin with several eminences in proximal half. P2 merus three-quarters length of carapace, as long as P2 propodus; P3 merus 0.8 × length of P3 propodus; P4 merus 0.7 × length of P4 propodus. Carpi short relative to breadth, successively slightly shorter posteriorly, length one-third that of propodus on P2 and P3, one-fourth on P4. Propodi subequal on P2 and P3, slightly longer on P4; flexor margin with paired terminal spines only. Dactyli subequal on P2 and P3, slightly longer on P4; length 2.3-2.4 × breadth (breadth measured at base); dactylus-carpus length ratio, 1.4 on P2, 1.5 on P3, 1.7 on P4, and 0.5 × length of propodi on P2, slightly less than so on P4; relatively stout, slightly curving distally; flexor margin with 6 spines on P2, 6 or 7 on P3, 7 on P4, ultimate spine very slender and short, obscured by fine setae, very close or nearly contiguous to very broad penultimate spine, remaining spines slender, loosely arranged and obliquely directed; penultimate spine 9 × broader than ultimate, 5 × broader than antepenultimate.

REMARKS — The species is similar to U. paenultimus Baba, 2005 and U. volsmar n. sp. in having the anterolateral spine of the carapace very close to the lateral orbital spine, in having a short antennal scale, in having sternite 3 with the posterolateral margin relatively long, and in having the P2-4 dactyli with the penultimate spine prominent and preceded by slender spines. Uroptychus laurentae is differentiated from U. paenultimus by: the rostrum that is much longer instead of slightly shorter than broad; article 4 of the antennal peduncle that is unarmed instead of bearing a distinct distomesial spine; sternite 4 that has the posterolateral margin distinctly longer instead of slightly shorter than the anterolateral margin; the P2-4 dactyli that are shorter relative to breadth (the length-breadth ratio 2.3-2.4 versus 3.1-3.4) and that bear the penultimate spine much greater, being 9 times instead of 5 times as long as the ultimate spine. Differences between U. laurentae and U. volsmar are mentioned under the remarks of the latter (see below).

The new species also resembles U. longicheles Ahyong & Poore, 2004 in having the anterolateral spine of the carapace close to the lateral orbital spine and in the spination of the P2-4 dactyli. However, U. laurentae is distinctive in having the branchial lateral margin with 6 instead of 4 or 5 spines, in having the rostrum 1.4 times longer instead of slightly shorter than broad, in having the anterolateral spine of the carapace subequal to instead of smaller than the lateral orbital spine, in having sternite 4 with the posterolateral margin distinctly longer than instead of subequally long as the anterolateral margin, and in having the antennal article 2 unarmed instead of bearing a distolateral spine.

Figures

FIGURE 123 Uroptychus laurentae n. sp., holotype, male 2.9 mm (MNHN-IU-2014-16617). A, carapace and abdomen, dorsal. B, same, lateral. C, sternal plastron,with excavated sternum and basal parts of Mxp1.D, telson.E, right antenna,ventral.F, left Mxp3,setae omitted, ventral.G, same, lateral.H, right P1, dorsal.I, left P1, distal part,dorsal. Scale bars: 1 mm.

FIGURE 124 Uroptychus laurentae n. sp., holotype, male 2.9 mm (MNHN-IU-2014-16617). A, right P2, lateral. B, same, distal part, lateral.C, right P3, setae omitted, lateral. D, right P4, setae omitted,lateral.Scale bars:1 mm.