Uroptychus boisselierae, 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 : 109-112

Uroptychus boisselierae n. sp.

Figures 39 , 40

TYPE MATERIAL — Holotype: Vanuatu. MUSORSTOM 8 Stn CP 1088, 15°09.23’S, 167°15.13’E, 425-455 m, 6.X.1994, ♂ 7.5 mm ( MNHN-IU-2014-16333 ) . Paratypes: Vanuatu. MUSORSTOM 8 Stn CP982, 19°21.80’S, 169°26.47’E, 408- 410 m, 23.IX.1994, 1 ♂ 4.0 mm, 1 ♀ 6.6 mm (MNHN-IU-2014-16334).

ETYMOLOGY„ Named for Marie-Catharine Boisselier of MNHN for her help with molecular analyses.

DISTRIBUTION„ Vanuatu; 408- 455 m.

DESCRIPTION„ Medium sized-species. Carapace: As long as broad; greatest breadth 1.6 × distance between anterolateral spines. Dorsal surface polished and glabrous, somewhat convex from anterior to posterior, with shallow depression between gastric and cardiac regions; epigastric region with pair of denticulate ridges; a few denticle-like spines mesial to anterior end of branchial lateral margin. Lateral margins slightly convexly divergent posteriorly, ridged along posterior fifth of length; 2 strong spines: first anterolateral, moderately distant from, distinctly posterior to level of, and overreaching small lateral orbital spine; second situated at anterior end of branchial margin, preceded by 1 or 2 tiny spines, followed by a few to several small spines or tubercle-like processes. Rostrum sharp triangular, with interior angle of 30-35°; length slightly less than half that of carapace, breadth more than half carapace breadth measured at posterior carapace margin; dorsal surface concave, ventral surface horizontal, lateral margins straight. Pterygostomian with anterior margin more or less roundish ending in small spine; surface smooth.

Sternum: Excavated sternum with small spine in center, anterior margin broad triangular. Sternal plastron slightly shorter than broad, with posteriorly divergent lateral extremities. Sternite 3 strongly depressed; anterior margin deeply excavated, with narrow U-shaped median notch separating 2 well-developed submedian spines. Sternite 4 having anterolateral margin convex, anteriorly ending in short blunt spine or process followed by a few posteriorly diminishing small spines; posterolateral margin half as long as anterolateral margin. Anterolateral margins of sternite 5 convexly somewhat divergent posteriorly, 1.3 × longer than posterolateral margin of sternite 4.

Abdomen: Smooth and barely setose. Somite 1 transversely ridged. Somite 2 tergite 2.7-2.9 × broader than long; pleuron posterolaterally angular, lateral margin concavely moderately divergent posteriorly. Pleuron of somite 3 with angular posterolateral end. Telson about half as long as broad; posterior plate 1.5 × longer than anterior plate, laterally expanded and lobed, posterior margin deeply emarginate.

Eye: Elongate, 2 × as long as broad, overreaching midlength of rostrum; mesial margin somewhat convex proximally. Cornea not dilated, length slightly more than half that of remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 2.2-2.7 × longer than high. Antennal peduncle slightly overreaching cornea. Article 2 with very small distolateral spine. Antennal scale twice as broad as article 5, reaching or slightly falling short of distal end of article 5. Articles 4 and 5 each with distomesial spine. Article 5 2.3 × longer than article 4, breadth half height of antennular ultimate article. Flagellum consisting of 18-24 segments, reaching distal end of P1 merus.

Mxp: Mxp1 with bases close to each other. Mxp3 barely setose on lateral face. Basis with 3 or 4 denticles on mesial ridge. Ischium having flexor margin not rounded distally, crista dentata with 18-25 denticles. Merus 2 × longer than ischium; distolateral spine small; flexor margin sharply ridged, bearing small spine distal to midlength. Carpus with small distolateral spine and another small spine on extensor proximal margin.

P1: Somewhat massive in larger male, 3.8 × (smaller male), 5.2 × (larger male), 4.7 × (female) longer than carapace; barely setose on proximal articles, sparingly setose on carpus and palm, more setose on fingers. Ischium dorsally with strong spine, ventromesially with strong subterminal spine. Merus 1.1-1.2 × longer than carapace, polished, with spines of good size: 1 dorsal distomesial, 1 ventral distolateral, 1 ventral distomesial, 3 ventral in longitudinal row, 3-5 ventromesial, and 2-3 mesial (spination weak in holotype). Carpus ventrally flattish, dorsally with denticulate short ridges, ventrolaterally with tubercle-like spines, mesially with row of small spines; length 1.3 × (0.95 × in male paratype) that of merus. Palm moderately depressed, 2.3-2.6 × longer than broad, subequal to length of carpus, ridged on mesial and lateral margins, with row of 8 or 9 small spines (continued on proximal part of fixed finger) along ventrolateral margin (not visible in dorsal view) in male holotype and female paratype, obsolescent in male paratype. Fingers distally incurved, crossing when closed; movable finger 0.5-0.6 × as long as palm, opposable margin with pronounced process proximal to opposite eminence on fixed finger.

P2-4: Slender, somewhat compressed mesio-laterally, sparsely with simple long setae. Meri successively shorter posteriorly (P3 merus 0.9 × length of P2 merus (P2 and P3 meri subequal in male paratype), P4 merus 0.8-0.9 × length of P3 merus), equally broad on P2-4; length-breadth ratio, 5.9-6.2 on P2, 5.7-6.0 on P3, 4.4-4.8 on P4; dorsal margin not cristate but rounded, with several small spines on proximal portion on P2 and P3 (obsolescent in male paratype); P2 merus subequal to (holotype and female paratype) or slightly shorter than (male paratype) carapace, 1.5-1.6 × longer than P2 propodus; P3 merus 1.3 × length of P3 propodus; P4 merus subequal to or slightly longer than P4 propodus. Carpi unarmed; P3 carpus slightly longer than P2 carpus (subequal in smaller male), P4 carpus subequal to P3 carpus; carpus-propodus length ratio, 0.7-0.8 on P2, 0.6-0.7 on P3, 0.6 on P4; carpus-dactylus length ratio, 2.2 on P2, 2.4 on P3, 2.6 on P4. Propodi successively slightly shorter posteriorly; flexor margin slightly convex on distal half, with pair of terminal spines preceded by 7-12 spines along nearly entire length on P2, 7-8 spines on P3, 6-8 spines on P4. Dactyli subequal in length on P2 and P3 and longer on P4 or shortest on P2 and subequal on P3 and P4; length 0.4 × that of carpus and 0.3 × that of propodus on P2-4; extensor margin with plumose setae; flexor margin strongly curving at proximal third, with row of 9-10 sharp, somewhat obliquely directed spines successively diminishing toward base of article and obscured by setae; ultimate and penultimate spines subequal and nearly as broad as antepenultimate.

REMARKS — The spination of the carapace lateral margin and P2-4, propodi and dactyli in particular, and the shape of sternite 3 in the new species resemble those of U. longicarpus n. sp. (see below). Uroptychus longicarpus is unique among the species of the genus in having the P4 carpus distinctly longer than the P3 carpus. Uroptychus boisselierae differs from U. longicarpus in having the epigastric region of the carapace with a pair of denticulate ridges instead of being smooth; the anterolateral margin of sternite 4 is twice instead of three to four times the length of posterolateral margin; the antennal article 4 bears a distinct distomesial spine instead of being unarmed; the corneas are not inflated as in U. longicarpus ; the P1 merus is spinose instead of granulose on the ventral surface, and the ischium bears a distinct subterminal spine instead of being unarmed on the ventromesial margin; and the P2-4 dactyli bears the ultimate spine subequal to instead of larger than the penultimate spine.

Figures

FIGURE 39 Uroptychus boisselierae n.sp.,holotype,male 7.5 mm (MNHN-IU-2014-16333).A, carapace and anterior part of abdomen,proximal part of P1 included, dorsal.B, same,lateral.C, sternal plastron,with excavated sternum and basal parts of Mxp1.D, telson. E, left antenna,ventral. F, left Mxp3,setae omitted, ventral. G, same,lateral.H, right P1, proximal part, setae omitted, ventral.I, same, dorsal. Scale bars: A, B, H, I, 5 mm; C-G, 1 mm.

FIGURE 40 Uroptychus boisselierae n. sp., holotype, male 7.5 mm (MNHN-IU-2014-16333). A, left P2, lateral. B, same, distal part, setae omitted, lateral. C, left P3, setae omitted, lateral. D, same, distal part, setae omitted, lateral. E, left P4, setae omitted, lateral. F, same, distal part, setae omitted, lateral. Scale bars: 1 mm.