Uroptychus corbariae, 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 : 142-145

Uroptychus corbariae n. sp.

Figures 56 , 57

TYPE MATERIAL — Holotype: Indonesia, Kai Islands . KARUBAR Stn CP 19, 5°15’S, 133°01’E, 605- 576 m, on gorgonian coral, 25.X.1991, ♂ 5.3 mm ( MNHN-IU-2014-16361 ) . Paratype: Collected with holotype, 1 ov. ♀ 5.4 mm ( MNHN- IU-2014-16362) .

DISTRIBUTION„ Kai Islands, Indonesia, 605- 576 m.

ETYMOLOGY„ Dedicated to Laure Corbari of MNHN for her help and support.

DESCRIPTION„ Medium-sized species. Carapace: Broader than long (0.8-0.9 × as long as broad); greatest breadth 1.4-1.9 × distance between anterolateral spines. Dorsal surface smooth, somewhat convex from anterior to posterior, feebly depressed between gastric and cardiac regions, bearing pair of low blunt epigastric spines; ridged along posterior third of lateral margin. Lateral margins gently constricted at anterior third; anterior part (anterior to constrictions) gently divergent posteriorly, with 2 well-developed spines, first anterolateral spine directed straight forward or slightly anteromesially, overreaching base of antennal scale, second short, situated at anterior end of anterior branchial region, nearly smooth without distinct spine between first and second; posterior part (posterior to constrictions or posterior branchial margin) gently convex, bearing short blunt spine at anterior end of posterior branchial margin or at midlength of carapace lateral margin, followed by obsolescent crenulations. Rostrum narrow triangular, directed somewhat dorsally or straight horizontal, with interior angle of 21°; slightly longer (male) or slightly shorter (female) than broad; dorsal surface concave; length 0.4 × (male) or 0.3 × (female) that of remaining carapace; breadth much less than half carapace breadth measured at posterior carapace margin. Lateral orbital spine small, slightly anterior to level of anterolateral spine. Pterygostomian flap anteriorly angular, produced to strong spine, with 3-5 small spines on anterior surface; height of posterior half slightly more than half that of anterior half.

Sternum: Excavated sternum with sharp ridge in midline, anterior margin produced triangularly between bases of Mxp1. Sternal plastron 1.4 or 1.5 × broader than long, lateral extremities convexly divergent behind sternite 4, sternite 7 slightly narrower than sternite 6. Sternite 3 shallowly depressed; anterior margin moderately concave, with deep, narrow U-shaped median notch. Sternite 4 broad relative to length; anterolateral margin anteriorly convex, length 1.4-1.6 × that of posterolateral margin. Sternite 5 with convex anterolateral margin as long as posterolateral margin of sternite 4.

Abdomen: Somites short relative to breadth. Somite 1 with antero-posteriorly convex transverse ridge. Somite 2 tergite 2.9 × longer than broad, pleuron posterolaterally produced more bluntly on male than on female. Pleura of somites 3-4 laterally more rounded in male than in female. Telson 0.4 × as long as broad; posterior plate 1.3-1.6 × longer than anterior plate, posterior margin slightly emarginate.

Eye: Elongate, 1.8 × longer than broad, reaching distal quarter of rostrum, slightly narrowed medially. Cornea slightly dilated, much more than half length of remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 3.1-3.3 × longer than high. Antennal peduncle reaching or overreaching apex of rostrum. Article 2 with short distolateral spine. Antennal scale proportionately broad, distally rounded or blunt, 1.5 × broader than article 5, slightly overreaching article 4 or reaching proximal third of length of article 5. Article 4 unarmed. Article 5 also unarmed, length 1.4 × that of article 4, breadth 0.5 × height of ultimate article of antennule. Flagellum of 14 segments not reaching distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 basis without denticle on mesial ridge. Ischium with flexor margin distally rounded, crista dentata with about 20 minute (obsolescent) denticles. Merus twice as long as ischium, mesial face flattish; flexor margin roundly ridged on proximal half, sharply ridged on distal half, bearing 1 or 2 very short, blunt spines on distal third; lateral face with short blunt distal spine. Carpus unarmed. P1: 5.3 × (female), 6.4 (male) longer than carapace, smooth and barely setose except for fingers. Ischium with strong dorsal spine with or without small accompanying spine proximally; ventromesial margin with subterminal spine very short and blunt, not reaching distal end of ischium, proximally with obsolescent protuberances. Merus with 2-4 obsolescent, low, blunt spines along mesial margin, blunt distomesial spine on dorsal surface, and blunt distomesial spine on ventral surface; length 1.3 or 1.4 × that of carapace. Carpus 1.4 × length of merus, with no spine laterally and mesially. Palm unarmed, depressed, 0.6 × as high as broad, lateral and mesial margins subparallel, somewhat narrowed proximally; 4.4-3.5 × as long as broad. Fingers relatively slender distally, sparingly setose, moderately gaping in proximal two-thirds in male, not gaping in female, distally not clearly crossing; fixed finger directed laterally in male, not distinctly so in female; movable finger 0.4 × as long as palm, opposable margin with prominent process (distal margin of process perpendicular to opposable margin in male) fitting into narrow longitudinal groove on opposite ventromesial face of fixed finger when closed.

P2-4: Relatively slender, well compressed, sparsely with simple setae, more setose on dactyli. Ischia with 2 short dorsal spines. Meri subequal in length on P2 and P3 or very slightly shorter on P3 than on P2, shortest on P4 (P4 merus 0.6 × length of P3 merus); subequally broad on P2 and P3, very slightly narrower on P4; dorsal margin unarmed; lengthbreadth ratio, 4.3 (male) or 4.8 (female) on P2, 4.3 on P3, 2.9 (male) or 3.1 (female) on P4; P2 merus 0.9 × (male) or 0.8 × (female) length of carapace, subequal to or very slightly longer than P2 propodus; P3 merus subequal to length of P3 propodus. P4 merus 0.7 × (female) or 0.8 × (male) length of P4 propodus. Carpi subequal in length on P2 and P3 (female) or slightly longer on P2 than on P3 (male), shortest on P4 (P4 carpus 0.7 × (female) or 0.8 × (male) length of P3 carpus), 0.5 × length of propodus on P2, 0.4 × (male) or 0.5 × (female) on P3, slightly less than 0.4 × on P4. Propodi subequal on P2 and P3, shortest on P4; flexor margin slightly concave in lateral view, with pair of slender terminal spines only. Dactyli subequal in length on P2-4; dactylus-carpus length ratio, 1.0 on P2, 1.0-1.1 on P3, 1.4-1.5 on P4; dactylus-propodus length ratio, 0.5 on P2 and P3, 0.5-0.6 on P4; flexor margin slightly curving, with 7 sharp spines loosely arranged, proximally diminishing and nearly perpendicular to margin, ultimate spine slightly more slender than penultimate.

Eggs. Number of eggs carried, 4; size, 1.08 × 1.46 mm - 1.25 × 1.42 mm.

REMARKS — Uroptychus corbariae resembles U. clarki n. sp. and U. defayeae n. sp. (see their similarities under the account of U. clarki ).

Uroptychus corbariae is distinguished from U. clarki by lacking spines between the first and second strong spines on the carapace lateral margin; the posterior branchial margin is crenulated (at most bearing a small spine) instead of bearing 4 or 5 spines; the epigastric region bears a pair of spines not flanked by two small spines; the antennal article 2 has a small distolateral spine, not pronounced as in U. clarki . The relationships with U. defayeae are discussed under the remarks of that species (see below).

The combination of the carapace lateral marginal spines restricted to the anterior half and the ultimate of the P2-4 dactylar spines more slender than the penultimate links this species to U. joloensis Van Dam, 1939 and U. zezuensis Kim, 1972 . However, Uroptychus corbariae is more distant from both than from the above-mentioned five congeners in having a pair of blunt, distinct epigastric spines and in having the penultimate and antepenultimate of the P2-4 dactylar spines relatively slender, not so strong as in U. joloensis and U. zezuensis .

Figures

FIGURE 56 Uroptychus corbariae n. sp., A-D, F-I, holotype, male 5.3 mm (MNHN-IU-2014-16361); E, paratype, ovigerous female 5.4 mm (MNHN-IU-2014-16362). A, carapace and anterior part of abdomen, proximal part of left P1 included, dorsal. B, same, lateral. C, sternal plastron, with excavated sternum and basal parts of Mxp1. D, right pleura of abdominal somites 2-4, dorsolateral. E, right pleura of abdominal somites 2-5, dorsolateral. F, telson. G, left antenna, ventral. H, right crista dentata, ventral. I, right Mxp3,lateral. Scale bars:1 mm.

FIGURE 57 Uroptychus corbariae n. sp., holotype, male 5.3 mm (MNHN-IU-2014-16361).A, left P1, dorsal. B, same,proximal part, ventral. C, right P2, lateral. D, same,distal part,setae omitted,lateral. E, right P3, setae omitted, lateral. F, right P4,setae omitted, lateral. Scale bars:1 mm.