Uroptychus latirostris Yokoya, 1933

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 : 264-266

Uroptychus latirostris Yokoya, 1933

Figure 122

Uroptychus latirostris Yokoya, 1933: 69 , figs 30. — Baba 2005: 39, figs 11-12.

TYPE MATERIAL — Neotype: Japan, Ashizuri-zaki , Tosa Bay, 150 m, male ( ZLKU 12993 ). [not examined].

MATERIAL EXAMINED — New Caledonia, Hunter and Matthew Islands. VOLSMAR Stn DW39, 22°20’S, 168°44’E, 280-305 m, 08.VI.1989, 1 ♂ 3.3 mm (MNHN-IU-2014-16612) . New Caledonia, Norfolk Ridge. SMIB 8 Stn DW183, 23°18’S, 168°05’E, 330-367 m, 31.I.1993, 1 ♂ 4.3 mm (MNHN- IU-2014-12791). – Stn DW190, 23°18’S, 168°05’E, 305-310 m, 31.I.1993, 3 ♂ 3.2-4.0 mm (MNHN-IU-2014-12792) . Vanuatu. MUSORSTOM 8 Stn CP1017, 17°52.80’S, 168°26.20’E, 294-295 m, 27.IX.1994, 1 ov. ♀ 4.2 mm (MNHN-IU-2014-16613) . Solomon Islands. SALOMON 2 Stn CP2179, 8°48.6’S, 159°43.3’E, 765-773 m, 22.X.2004, 1 ♂ 3.8 mm (MNHN-IU-2014-16614) . Indonesia, Tanimbar Islands. KARUBAR Stn DW50, 7°59’S, 133°02’E, 184-186 m, 29.X.1991, 2 ov. ♀ 5.5, 5.6 mm, 1 ♀ 5.3 mm (MNHN-IU-2014-16615) . Philippines. MUSORSTOM 2 Stn DR33, 13°32’N, 121°07’E, 130- 137 m, with Chrysogorgia sp. ( Calcaxonia , Chrysogorgiidae ), 24.XI.1980, 3 ov. ♀ 4.2-6.0 mm, 1 ♀ 3.7 mm (MNHN-IU-2014-16616) .

DISTRIBUTION„ Previously known from Sagami Bay, Izu Islands, Bonin [Ogasawara] Islands, and Tosa Bay ( Japan); 100- 200 m. The present material is from the Philippines, Indonesia, Vanuatu, Hunter-Matthew Islands, and Norfolk Ridge, in 130- 773 m.

SIZE„ Males, 3.2-4.3 mm; females, 3.7-6.0 mm; ovigerous females from 4.2 mm.

DIAGNOSIS — Small to medium-sized species. Carapace as long as or slightly longer than broad; greatest breadth 1.3- 1.4 × distance between anterolateral spines. Dorsal surface smooth and glabrous. Lateral margins slightly convex on posterior branchial region, bearing 3 spines: first anterolateral, reaching or slightly overreaching tip of smaller lateral orbital spine; second larger than first, placed on anterior end of anterior branchial region, followed by tiny third. Rostrum broad triangular, with interior angle of 49-51°; dorsal surface deeply concave; length about half postorbital carapace length, breadth three-quarters carapace breadth at posterior carapace margin. Lateral orbital spine directly mesial and close to anterolateral spine. Pterygostomian flap anteriorly roundish with small spine. Excavated sternum anteriorly produced to sharp subtriangular spine between close bases of Mxp1. Sternal plastron as long as broad; sternite 3 with deeply concave anterior margin without distinct submedian spines, occasionally with rudimentary spines; sternite 4 with anterolateral margin somewhat convex, about 4 × longer than posterolateral margin. Anterolateral margin of sternite 5 more than 5 × longer than posterolateral margin of sternite 4. Abdominal somites smooth, without transverse ridge on somite 1. Somite 2 tergite 2.3-2.5 × broader than long; pleuron posterolaterally strongly divergent, ending in blunt margin; pleuron of somite 3 posterolaterally blunt. Telson 0.6 × as long as broad; posterior plate semicircular or with concave posterior margin, length 1.7-1.9 × that of anterior plate. Eyes elongate, nearly reaching rostral tip; cornea half as long as remaining eyestalk. Ultimate article of antennule high relative to length, length 1.9-2.3 × height. Antennal peduncle terminating at distal end of cornea; article 2 with tiny lateral spine; antennal scale reaching or overreaching midlength of article 5, not reaching distal end of that article; article 5 with small distomesial spine, length 2.0-2.2 × that of article 4, breadth 0.3-0.5 that of antennular ultimate article; flagellum of 20-23 segments reaching or slightly overreaching distal end of P1 merus.

Mxp3 basis with a few denticles on mesial ridge, distalmost constant, others often obsolescent; ischium with 20-22 denticles on crista dentata, flexor margin distally not rounded; merus 2.0-2.3 × longer than ischium, P1 4.2-6.2 × longer than carapace, moderately massive, denticulate on proximal portion of merus, smooth elsewhere; ischium with long sharp dorsal spine, no spine elsewhere; merus 1.2-1.4 × longer than carapace; carpus 1.3-1.5 × length of merus, terminal margin with dorsal spine medially; palm 2.1-2.4 × (males), 3.2-4.9 × (females) longer than broad, varying from slightly shorter to slightly longer than carpus; fingers distally incurved, crossing when closed, with obtuse process on opposable margin of movable finger; movable finger 0.4-0.5 × length of palm. P2-4 relatively slender, with long, coarse setae on distal articles; meri successively shorter posteriorly (P3 merus 0.91-0.96 × length of P2 merus, P4 merus 0.84-0.85 × length of P3 merus), subequally broad on P2-4, length-breadth ratio, 5.6-6.0 on P2, 4.6-5.4 on P3, 4.2-4.3 on P4; P2 merus 1.0- 1.3 × length of carapace, 1.6-1.7 × length of P2 propodus; P4 merus as long as or slightly longer than P4 propodus; carpi subequal; carpus-propodus length ratio, 0.6 on P2 and P3, 0.5-0.6 on P4; propodi having flexor margin terminating in pair of spines preceded by 8 spines on P2, 7 on P3, 6-7 on P4; dactyli shorter than carpi (dactylus-carpus length ratio, 0.6 on P2, 0.7 on P3, 0.7-0.8 on P4), 0.4 × as long as propodi on P2-4; flexor margin strongly curving at proximal third, with 9-10 successively diminishing subtriangular spines, ultimate largest.

Eggs. Number of eggs carried, up to 28; size, 1.28 mm × 1.06 mm - 1.24 mm × 1.04 mm.

REMARKS — The specimens examined agree well with the description of neotype ( Baba 2005), except for the following: the posterior plate of the telson is slightly convex on the posterior margin in two of the three males from the Norfolk Ridge (MNHN-IU-2014-12792), whereas in the male from Vanuatu it is concave; the antennal scale is as in the neotype, terminating in the midlength of article 5 in the smallest male from the Norfolk Ridge, whereas in the other specimens it distinctly overreaches the midlength but barely reaches the distal end of that article. These differences are here considered as intraspecific variations. There still remains a problem with the systematic status of Uroptychus cavirostris Alcock and Anderson, 1899 , which has been regarded to be different from U. latirostris in having the emarginate posterior margin of the telson. The material reported by Tirmizi (1964) from the western Indian Ocean, which was examined on loan from the Natural History Museum, London, is referable to an undescribed species, having a distally narrowed rostrum, in having a pair of median spines on the sternite 3 anterior margin, and in having an anterior branchial marginal spine vestigial rather than well developed. The Vanuatu material here examined occasionally has a concave posterior margin of telson just as defined for U. cavirostris . Access to the type material of U. cavirostris is now hardly possible, so discovery of topotypic material would solve the problem.

The elongate eyes, broad rostrum, spination of both the carapace lateral margin and P2-4 displayed by the present species are much like those of U. alcocki Ahyong & Poore, 2004 and U. yokoyai Ahyong & Poore, 2004 . Their relationships are discussed under U. yokoyai (see below).

Figures

FIGURE 122 Uroptychus latirostris Yokoya, 1933, ovigerous female 4.2 mm (MNHN-IU-2014-16613). A, carapace and anterior part of abdomen, proximal part of left P1 included, dorsal.B, anterior part of sternal plastron.C, telson.D, right P2,lateral. E, same, distal part, setae omitted, lateral.Scale bars: 1 mm.