Uroptychus brachycarpus, 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 : 113-116

Uroptychus brachycarpus n. sp.

Figures 41 , 42

TYPE MATERIAL — Holotype: New Caledonia, Norfolk Ridge. SMIB 4 Stn DW61, 23°01’S, 167°22’E, 520-550 m, 10.III.1989, with Chrysogorgiidae gen. sp. ( Calcaxonia ), sex indet., 7.5 mm ( MNHN-IU-2014-16335 ) . Paratypes: New Caledonia, Norfolk Ridge. MUSORSTOM 4 Stn CP216, 22°59.5’S, 167°22.0’E, 490-515 m, with Chrysogorgiidae gen. sp. ( Calcaxonia ), 29.IX.1985, 2 ♂ 6.3, 7.2 mm, 1 ov. ♀ 8.7 mm (MNHN-IU-2014-16338) . SMIB 8 Stn DW194, 22°59.6’S, 168°22.5’E, 491 m, 1.II.1993, 1 ♀ 8.3 mm (MNHN-IU-2014-16339) . BIOCAL Stn CP52, 23°06’S, 167°47’E, 540-600 m, 31.VIII.1985, 1 ♂ 6.3 mm, 1 ov. ♀ 6.9 mm, 1 ♀ 4.4 mm (MNHN-IU-2014-16340) . Indonesia, Kai Islands. KARUBAR Stn CP05, 5°49’S, 132°18’E, 296-299 m, 22.X.1991, with? Acanella sp. ( Calcaxonia : Isididae ), 1 ♂ 6.2 mm, 1 ov. ♀ 7.5 mm (MNHN-IU-2014-16336) . Vanuatu. MUSORSTOM 8 Stn CP1088, 15°09.23’S, 167°15.13’E, 425-455 m, 6.X.1994, 3 ov. ♀ 7.7-8.8 mm, 1 ♀ 6.5 mm (MNHN-IU-2014-16337) .

ETYMOLOGY„ From the Greek brachys (short) and carpos (carpus, wrist), referring to short carpi of P2-4, by which the species is distinguished from the related species U. brucei .

DISTRIBUTION„ South of New Caledonia, Isle of Pines, Vanuatu, and Kai Islands ( Indonesia); 296- 600 m.

SIZE„ Males, 6.2-7.2 mm; females, 4.4-8.8 mm; ovigerous females from 6.9 mm.

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 smooth and glabrous, slightly convex from anterior to posterior, with weak or indistinct depression between gastric and cardiac regions; covered with small circular spots (visible but not hollowed out), and with granulations along lateral margins, more distinctly on anterior part in large specimens. Lateral margins convexly divergent posteriorly, bearing granules or denticles on anterior third, ridged along branchial region; anterolateral spine relatively large, overreaching small lateral orbital spine. Rostrum elongate triangular, with interior angle of 30°, dorsally excavated and somewhat deflected ventrally; lateral margins feebly convex anteriorly; length 0.3-0.5 that of remaining carapace, breadth less than half carapace breadth measured at posterior carapace margin. Lateral orbital spine situated at same level as, and more or less remote from, anterolateral spine. Pterygostomian flap anteriorly sharp angular, produced to small spine; surface granulose.

Sternum: Excavated sternum with convex anterior margin between bases of Mxp1, surface with rounded ridge in midline. Sternal plastron 0.9 × as long as broad, lateral extremities divergent posteriorly. Sternite 3 depressed well, anterolaterally sharp angular, anterior margin shallowly concave, with V-shaped median notch flanked by small spine. Sternite 4 having anterolateral margins nearly straight or anteriorly convex, anterior end rounded, often with granules or denticles; posterolateral margin short, about half as long as anterolateral margin. Anterolateral margin of sternite 5 anteriorly strongly convex, slightly more than 1.5 × longer than posterolateral margin of sternite 4.

Abdomen: Smooth and almost glabrous. Somite 1 convex from anterior to posterior, without transverse ridge. Somite 2 tergite 2.4-2.8 × broader than long; lateral margins somewhat concavely divergent and posteriorly rounded. Pleuron of somite 3 posterolaterally blunt. Telson half as long as broad; posterior plate nearly transverse or slightly emarginate on posterior margin, length subequal to or slightly more than that of anterior plate.

Eye: Relatively elongate, slightly less than 2 × longer than broad, slightly broadened proximally, overreaching midlength of rostrum. Cornea not inflated, more than half that of remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 3.0-3.3 × longer than high. Antennal peduncle overreaching cornea, not reaching apex of rostrum. Article 2 with short, sharp distolateral spine. Antennal scale more than twice as broad as article 5, slightly falling short of (rarely reaching) distal end of article 5. Article 4 with small distomesial

spine. Article 5 unarmed, 1.6-1.7 × longer than article 4, breadth 0.7 × height of ultimate article of antennule. Flagellum of 15-22 segments barely reaching distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 basis smooth on mesial ridge. Ischium with distally diminishing small denticles on crista dentata; flexor margin sharply ridged, distally rounded. Merus 2.2 × longer than ischium, compressed well, mesially flattish, flexor margin angular at point one-third from distal end, with 3-5 tubercle-like spines distal to angular portion. Carpus unarmed.

P1: Massive, unarmed, nearly glabrous except for fingers; length 4.4-4.9 × that of carapace. Ischium dorsally with basally broad, antero-posteriorly flattish, distally sharp spine, ventromesially with row of low processes on proximal portion, without distinct subterminal spine. Merus 1.0-1.1 × longer than carapace, weakly granulose on proximal portions of ventral and mesial surfaces. Carpus 1.0-1.4 × longer than merus. Palm 2.2-2.4 × (males), 2.8-3.5 × (females) longer than broad, 1.0-1.3 × longer than carpus. Fingers depressed, sparingly with relatively short setae, not crossing distally; movable finger with subtriangular process on opposable median margin fitting to opposing concavity of fixed finger when closed; length about half or slightly less than half that of palm.

P2-4: Broad relative to length, well compressed mesio-laterally, setose barely on meri and carpi, sparsely on propodi, thickly on dactyli, setae relatively short. Meri and carpi unarmed. Meri successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.8 × length of P3 merus), equally broad on P2-4; length-breadth ratio, 3.4-3.8 on P2, 3.2-4.0 on P3, 3.0-3.5 on P4; P2 merus 0.8 × length of carapace, 1.2 × (rarely 1.1 ×) longer than P2 propodus; P3 merus 1.1 × length of P3 propodus; P4 merus 0.8 × length of P4 propodus. Carpi successively slightly shorter posteriorly (P3 carpus 0.92-0.96 × length of P2 carpus, P4 carpus 0.92-0.96 × length of P3 carpus), less than half length of propodi (0.41- 0.48 on P2, 0.37-0.41 on P3, 0.33-0.40 on P4). Propodi shorter on P2 than on P3 and P4, subequal on P3 and P4; flexor margin ending in pair of movable spines preceded by 3-5 spines on P2, 1-3 on P3, 0 or 1 on P4. Dactyli about half length of propodi, slightly (at most 1.1 x) longer than or subequal to carpi on P2-4; setae on extensor margin plumose; flexor margin slightly curving, with 9 or 10 well-developed, loosely arranged, proximally diminishing spines, all subtriangular, slightly obliquely directed, ultimate much more slender than penultimate, antepenultimate broader than ultimate and narrower than penultimate.

Eggs. About 50 eggs carried; size, 1.09 mm × 1.21 mm - 1.16 mm × 1.26 mm.

Parasites. The holotype bears an externa of rhizocephalan parasite on the abdomen.

REMARKS — This species keys out in a couplet together with U. amabilis Baba, 1977 from New Caledonia, sharing the carapace lateral margin with a well-developed anterolateral spine only, sternite 3 with a median notch on the anterior margin, the ultimate spine of the P2-4 more slender than the penultimate, and the P4 merus with a pair of terminal spines only on the flexor margin. However, they differ from each other in the spination of the P2-4 dactyli. Uroptychus brachycarpus has on the flexor margin, excepting the slender ultimate spine, a row of 8 or 9 long triangular, obliquely directed, proximally diminishing spines, whereas these spines in U. amabilis are less numerous (5 in number), short triangular and perpendicularly directed, the penultimate and antepenultimate being relatively broad. In addition, the Mxp3 merus in U. brachycarpus bears tubercle-like small spines only on the distal half of the flexor margin, whereas in U. amabilis this article bears a few distinct flexor marginal spines and a well-developed distolateral spine.

Uroptychus brachycarpus also resembles U. denticulisquama n. sp. in the carapace shape, in having a broad antennal scale, and in the spination of the P2-4 dactyli. Differences between these species are discussed under the remarks of U. denticulisquama (see below).

Figures

FIGURE 41 Uroptychus brachycarpus n. sp., holotype, sex indet.7.5 mm (MNHN-IU-2014-16335). A, carapace and abdomen, small spots on right side omitted,dorsal.B, same,abdomen excluded,lateral.C, sternal plastron,with excavated sternum and basal parts of Mxp1.D, telson.E, right antenna,ventral.F, left Mxp3,ventral. G, right Mxp3,lateral.H, left P1, dorsal.I, same,proximal part, ventral.Scale bars:A-G,1 mm; H, I, 5 mm.

FIGURE 42 Uroptychus brachycarpus n. sp.,holotype, sex indet.7.5 mm (MNHN-IU-2014-16335).A, right P2,lateral. B, same,distal part, setae omitted, lateral.C, right P3,setae omitted, lateral. D, right P4, setae omitted,lateral.Scale bars:1 mm.