Uroptychus denticulisquama, 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 : 166-170

Uroptychus denticulisquama n. sp.

Figures 69 , 70

TYPE MATERIAL — Holotype: New Caledonia. MUSORSTOM 4 Stn CP 216, 22°59.5’S, 167°22.0’E, 490-515 m, gorgonacean coral, 29.IX.1985, ♂ 6.3 mm ( MNHN-IU-2014-16382 ) . Paratypes: New Caledonia. MUSORSTOM 4 Stn CP216, collected with holotype, 1 ov. ♀ 6.3 mm (MNHN-IU-2014-16383) . BATHUS 2 Stn CP735, 23°01’S, 166°56’E, 530-570 m, 13.V.1993, 1 ♂ 4.1 mm (MNHN-IU-2014-16384) , 1 ov. ♀ 4.8 mm (MNHN-IU-2014-16385). New Caledonia, Isle of Pines. SMIB 2 Stn DC26, 22°59’S, 167°23’E, 500-535 m, 21.IX.1986, 1 ov. ♀ 7.0 mm. (MNHN-IU-2014-16386).

ETYMOLOGY„ From the Latin denticulus (dim. of dens, tooth) and squama (scale), a noun in apposition, referring to the antennal scale with denticles on the lateral margin.

DISTRIBUTION„ New Caledonia and Isle of Pines; 490- 570 m.

SIZE„ Males, 4.1-6.3 mm; ovigerous females, 4.8-7.0 mm.

DESCRIPTION„ Medium-sized species. Carapace: About as long as broad; greatest breadth 1.5-1.7 × distance between anterolateral spines. Dorsal surface slightly convex from anterior to posterior, with or without feeble depression between gastric and cardiac regions and between gastric and branchial regions, smooth but feebly or sparsely tuberculose along lateral margins (denticles on hepatic region usually present), sparsely setose. Lateral margins somewhat convexly divergent posteriorly; anterolateral spine short, terminating in or slightly overreaching tip of lateral orbital spine, followed by denticles or tubercles (rarely 2 small spines, one at anterior end of branchial region and another at anterior end of posterior branchial region). Rostrum narrow triangular, with interior angle of 25-30°, nearly straight horizontal or directed slightly dorsally; length 0.3-0.4 × postorbital carapace length, breadth less than half carapace breadth measured at posterior carapace margin; dorsal surface slightly concave; lateral margin with a few obsolescent denticles near tip. Lateral orbital spine small, slightly anterior to level of and moderately remote from anterolateral spine. Pterygostomian flap anteriorly angular, produced to small spine, surface somewhat granulose, with sparse short setae.

Sternum: Excavated sternum subtriangularly produced anteriorly, with ridge in midline. Sternal plastron as long as or very slightly shorter than broad; lateral extremities gently divergent posteriorly. Sternite 3 distinctly depressed, anterior margin shallowly concave, with pair of tiny or obsolescent submedian spines separated by narrow or somewhat broad U-shaped sinus. Sternite 4 having anterolateral margin nearly straight, anteriorly ending in 1 or 2 small spines, length about twice that of posterolateral margin. Anterolateral margins of sternite 5 subparallel, anteriorly rounded, length 1.4 × that of posterolateral margin of sternite 4.

Abdomen: Smooth, sparsely setose. Somite 1 convex from anterior to posterior, forming rounded transverse ridge. Somite 2 tergite 3.6 × broader than long; pleural lateral margin concave, weakly divergent posteriorly, ending in angular tip. Pleuron of somite 3 posterolaterally angular. Telson half as long as broad; posterior plate distinctly or feebly emarginate on posterior margin, length 1.1-1.5 × that of anterior plate.

Eye: Elongate, 2.0 × longer than broad, barely reaching rostral tip; mesial margin somewhat concave proximally. Cornea not dilated, about half as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 2.7-3.2 × longer than high. Antennal peduncle reaching or slightly overreaching cornea. Article 2 with 1 or 2 lateral spines. Antennal scale relatively broad, fully twice as broad as article 5, reaching or slightly falling short of distal end of article 5; lateral margin with a few small spines and relatively long setae. Article 4 with small distomesial spine. Article 5 with small or obsolescent distomesial spine; length 1.5-1.7 × that of article 4, breadth 0.6 × height of ultimate article of antennule. Flagellum composed of 16-19 segments, fully or barely reaching distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 setose on lateral surface, setae long. Basis with a few obsolescent denticles on mesial ridge. Ischium with about 30 small denticles on crista dentata, flexor margin distally rounded. Merus 1.9 × longer than ischium, flattish on mesial face, bearing distolateral spine very small or obsolete; flexor margin well ridged with a few small spines on distal third, rounded on proximal two-thirds. Carpus with tiny or obsolescent distolateral spine.

P1: 4.6-5.5 × longer than carapace, covered with distally softened setae, those on carpus and merus arising from short scale-like ridges. Ischium dorsally armed with relatively short, basally broad, depressed spine, ventromesially with strong subterminal spine proximally followed by very small denticle-like spines obscured by setae. Merus 0.9-1.3 × length of carapace, mesially tuberculose, with well-developed mesial distoventral spine and several small spines on proximal mesial surface. Carpus 1.2-1.3 × longer than merus, mesially tuberculose, ventrally with short blunt distomesial and distolateral spines. Palm 2.5-2.6 × (male), 2.8-3.1 × (females) longer than broad, subequal to length of carpus. Fingers broad relative to length, distally somwewhat incurved, weakly crossing when closed; movable finger half as long as palm, opposable margin with bluntly triangular proximal process fitting to opposite longitudinal concavity ventromesial to between 2 prominences of fixed finger when closed.

P2-4: Thickly covered with long setae, on ventral and ventromesial surfaces in particular. Meri moderately compressed mesio-laterally, successively diminishing posteriorly (P3 merus 0.8-0.9 × length of P2 merus, P4 merus 0.8 × length of P3 merus), successively very slightly narrower posteriorly; length-breadth ratio, 2.9-4.0 on P2, 2.7-3.0 on P3, 2.6-3.3 on P4; several eminences on proximal half of dorsal crest and denticle-like small spines along ventromesial margin, both only on P2; P2 merus 0.8-0.9 × length of carapace, 1.1-1.2 × length of P2 propodus; P3 merus 0.9 length of P3 propodus; P4 merus 0.8 × length of P4 propodus. P2 carpus slightly longer than or subequal to P3 carpus, P4 carpus subequal to or slightly shorter than P3 carpus, each 0.4 × length of respective propodus. Propodi subequal on P3 and P4 and slightly shorter on P2, subequal on P2-4, or subequal on P2-3 and shorter on P4 than on P3; flexor margin nearly straight on P2, slightly curving on P3 and P4, with pair of terminal spines preceded by 5-9 slender movable spines at most on distal two-thirds on P2 and P3, 4-6 on P4. Dactyli moderately curving, as long as carpi on P2, 1.0-1.1 × longer on P3, 1.2-1.3 × longer on P4, and 0.4-0.5 × as long as propodi on P2-4; flexor margin with 9-10 sharp, somewhat inclined, loosely arranged spines, ultimate spine shorter and much more slender than penultimate, penultimate broader than antepenultimate.

Eggs. Number of eggs carried, 14-25 but normal number probably more; size, 1.16 mm × 1.32 mm - 1.32 mm × 1.49 mm.

REMARKS — The ovigerous female paratype (MNHN-IU-2014-16386) from SMIB 2 Stn DC26 has a very short rostrum barely reaching midlength of eyes so that the proximal limit of eye is visible in a dorsal aspect but the other characters agree quite well with those of the others. This rostrum is presumably broken.

The species resembles U. brachycarpus n. sp. in the shapes of the carapace, Mxp3, antenna and P2-4 dactyli. However, U. brachycarpus has no lateral spines on the antennal scale; the thoracic appendages (Mxp3 and P1-4) are less setose; the P2 merus lacks a row of ventromesial marginal spines; and the P4 propodus bears a pair of terminal spines only; all distinctive differences from U. denticulisquama .

Uroptychus denticulisquama somewhat resembles U. indicus Alcock, 1901 , one of the poorly known species (see Figure 217 ). However, the carapace in U. indicus is distinctly longer than broad and smooth on the lateral margin, the antennal articles 4 and 5 are unarmed, the antennal scale lacks lateral spines, and P2-4 look more slender.

Figures

FIGURE 69 Uroptychus denticulisquama n.sp.,holotype,male 6.3 mm (MNHN-IU-2014-16382).A, carapace and anterior part of abdomen,dorsal. B, same,lateral.C, sternal plastron,with excavated sternum andbasal parts of Mxp1.D,telson.E,left antenna,ventral.F,right Mxp3,setae omitted,ventral.G, same,lateral.H, left P1,dorsal.I, same,proximal part,setae omitted,ventral.Scale bars:A,B,H,5 mm; C-G,I, 1 mm.

FIGURE 70 Uroptychus denticulisquama n. sp., holotype, male 6.3 mm (MNHN-IU-2014-16382). A, left P2, lateral. B, same, merus, setae omitted, ventral. C, same,distal part,setae omitted, lateral. D, left P3, setae omitted, lateral. E, left P4, setae omitted, lateral.Scale bars:1 mm.

FIGURE 217 Uroptychus indicus Alcock,1901,syntype,ovigerous female 7.2 mm (ZSI 9328/9).A, carapace,dorsal.B, anterior part of sternal plastron.C, telson. D, left antenna,ventral.E, left Mxp3, setae omitted,lateral.F, right P1, distal part,dorsal.G, left P2,dactylus and propodus,setae omitted,lateral. H, same,distal part,lateral.Scale bars:1 mm.