Uroptychus magnipedalis, 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 : 294-297

Uroptychus magnipedalis n. sp.

Figures 137 , 138

TYPE MATERIAL — Holotype: Vanuatu. MUSORSTOM 8 Stn CP 1088, 15°09’S, 167°15’E, 425-455 m, 6.X.1994, ♂ 6.3 mm ( MNHN-IU-2014-16718 ) . Paratype: Collected with holotype, 1 ♂ 7.2 mm (MNHN-IU-2014-16719).

ETYMOLOGY„ From the Latin magnus (large) and pedalis (of the foot), referring to a massive P1 of the species.

DISTRIBUTION„ Vanuatu; 425- 455 m.

DESCRIPTION„ Medium-sized species. Carapace: Slightly broader than long (0.9 × as long as broad); greatest breadth 1.8 × distance between anterolateral spines. Dorsal surface almost glabrous, slightly granulate sparsely, somewhat convex from anterior to posterior, without depression between gastric and cardiac regions. Lateral margins convexly divergent, ridged along posterior half; anterolateral spine slightly overreaching much smaller lateral orbital spine, followed by 3 very small spines anterior to 1 relatively large (smaller than anterolateral spine) and a few very small spines on posterior branchial region. Rostrum moderately broad triangular, with interior angle of 26-28°; length 0.4-0.5 × that of remaining carapace, breadth less than half carapace breadth at posterior carapace margin; dorsal surface concave; lateral margin with 1 (2 on left side in holotype) subterminal spinule. Lateral orbital spine situated slightly anterior to level of anterolateral spine. Pterygostomian flap anteriorly angular, produced to acute spine; surface with very small sparse tubercles on anterior portion.

Sternum: Excavated sternum with weak ridge in midline, anterior margin strongly convex. Sternal plastron slightly broader than long, lateral extremities weakly divergent posteriorly. Sternite 3 moderately depressed; anterior margin shallowly concave, with deep, narrow V-shaped or U-shaped median notch without flanking spine. Sternite 4 with anterolateral margin convex and anteriorly lobe-like with a few denticles; posterolateral margin about half as long as anterolateral margin. Anterolateral margin of sternite 5 anteriorly strongly convex, 1.2 × longer than posterolateral margin of sternite 4.

Abdomen: Smooth, polished and glabrous. Somite 1 convex from anterior to posterior, without transverse ridge. Somite 2 tergite 2.7-3.0 × broader than long; pleuron anterolaterally and posterolaterally blunt or bluntly angular, lateral margin slightly concave and slightly divergent posteriorly. Pleura of somites 3 and 4 tapering to angular or blunt tip. Telson about half as long as broad; posterior plate convex on posterior margin, length 1.2 × that of anterior plate.

Eye: Twice as long as broad, slightly narrowed distally, reaching anterior third of rostrum. Cornea not dilated, half as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 2.6-3.0 × longer than high. Antennal peduncle overreaching cornea. Article 2 with strong distolateral spine. Antennal scale overreaching article 5, about twice as broad as that article. Distal 2 articles each with well-developed distomesial spine, that of article 4 with small accompanying spine in holotype. Article 5 1.4 × longer than article 4, breadth 0.6-0.7 × height of antennular ultimate article. Flagellum consisting of 15-16 segments, slightly falling short of distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 basis with 1 or 2 denticles on mesial ridge. Ischium bearing long setae lateral to rounded distal end of flexor margin; crista dentata with about 30 denticles. Merus 1.6 × longer than ischium; flexor margin convex, sharply ridged, bearing a few denticles on distal third. Carpus with obsolescent distolateral process.

P1: Massive, 4.2-4.5 × longer than carapace, sparingly bearing short, fine setae. Ischium dorsally with strong spine, ventromesially with row of tubercular processes, without subterminal spine. Merus slightly longer than carapace, ventrally bearing blunt distomesial and distolateral spines. Carpus 1.1-1.2 × longer than merus, with 2 distoventral spines. Palm unarmed, 1.9-2.1 × longer than broad, 1.2 × longer than carpus, breadth at midlength slightly more than distance between anterolateral spines of carapace. Fingers short relative to breadth, distally incurved, crossing when closed, not gaping; movable finger having opposable margin with blunt median process fitting to opposite concavity on fixed finger when closed, length half that of palm. P2-4: With short setae sparse on proximal articles, numerous on distal articles, moderately compressed mesiolaterally. Meri relatively flattened, successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.8 × length of P3 merus), breadths subequal on P2 and P3, P4 merus 0.9 × as broad as P3 merus; dorsal crest with several denticles or eminences distinct on P2, obsolescent on P3, absent on P4; length-breadth ratio, 3.3-3.5 on P2, 3.0-3.4 on P3, 2.9-3.1 on P4; P2 merus 0.8 × length of carapace, 1.0-1.2 × length of P2 propodus; P3 merus 0.9 × length of P3 propodus; P4 merus 0.8 × length of P4 propodus. P3 carpus 0.9 × length of P2 carpus, P4 carpus 0.9-1.0 × length of P3 carpus, less than half (0.42-0.45 on P2, 0.38-0.40 on P3, 0.36-0.38 on P4) length of propodi. Propodi subequal in length on P2 and P3, longer on P 4 in holotype, shortest on P2 and longer on P3 than on P 4 in paratype; flexor margin straight, ending in pair of spines preceded by 6-7 spines on P2, 4 spines on P3, 3 spines on P4. Dactyli slightly shorter on P2 than on P3 and P4, slightly shorter than carpi on P2, subequal to that article on P3 and P4, slightly less than half length of propodi on P2-4; flexor margin gently curving, ending in slender spine preceded by 7-8 relatively long, sharp spines loosely arranged, slightly obliquely directed, and successively diminishing proximally, ultimate more slender than penultimate, penultimate slightly larger than antepenultimate.

REMARKS — Uroptychus magnipedalis resembles U. baeomma n. sp. in having a subapical spine on each side of the rostrum, in having elongate eyes, and in the shapes of the P2-4, sternal plastron and Mxp3. However, this new species may be differentiated from that species by the carapace bearing only one instead of 5 well-developed spines on the branchial margin, the antennal peduncle bearing much stronger instead of obsolescent spine on each of the distal two articles, and the antennal scale overreaching rather than falling short of the distal end of article 5.

Figures

FIGURE 137 Uroptychus magnipedalis n. sp., holotype, male 6.3 mm (MNHN-IU-2014-16718). A, carapace and anterior part of abdomen, proximal part 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, right Mxp3, ventral.G, same, lateral.H, right P1, proximal part omitted, dorsal. Scale bars: A,B,H, 5 mm; C-G,1 mm.

FIGURE 138 Uroptychus magnipedalis n. sp., holotype, male 6.3 mm (MNHN-IU-2014-16718).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.