Uroptychus paenultimus Baba, 2005

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 : 366-369

Uroptychus paenultimus Baba, 2005

Figures 180 , 181

Uroptychus paenultimus Baba, 2005: 49 , fig. 17.

TYPE MATERIAL — Holotype: Indonesia, Kai Islands , 320 m, ov. female ( ZMUC CRU-11318 ). [not examined].

MATERIAL EXAMINED — Tonga. BORDAU 2 Stn DW1615, 23°03’S, 175°53’W, 482-504 m, 17.VI.2000, 1 ♀ 2.3 mm (MNHN-IU-2014-16833).

DISTRIBUTION„ Kai Islands, and now Tonga; 320- 504 m.

DESCRIPTION„ Small species. Carapace: Slightly broader than long (0.9 × as long as broad); greatest breadth 1.4 × distance between anterolateral spines. Dorsal surface moderately convex from anterior to posterior, without distinct groove, barely setose. Lateral margins medially convex, with anterolateral spine of good size followed by 7 or 8 very small spines; anterolateral spine close to and slightly posterior to level of lateral orbital spine, barely reaching tip of that spine; ridged along posterior third. Rostrum triangular, slightly shorter than broad, with interior angle of ca. 35°, straight horizontal; lateral margins smooth; dorsal surface concave; length about half that of remaining carapace, breadth slightly more than half carapace breadth at posterior carapace margin. Lateral orbital spine subequal in size to anterolateral spine. Pterygostomian flap anteriorly angular, produced to small spine; surface with very small spines.

Sternum: Excavated sternum with slightly convex anterior margin, surface ridged in midline. Sternal plastron 1.1 × longer than broad, lateral extremities subparallel. Sternite 3 moderately depressed, anterior margin of wide V-shape with small median notch. Sternite 4 having anterolateral margin slightly convex, anteriorly angular; posterolateral margin slightly shorter than anterolateral margin. Anterolateral margins of sternite 5 subparallel, anteriorly rounded, slightly shorter than posterolateral margin of sternite 4.

Abdomen: With sparse soft setae. Somite 1 convex from anterior to posterior. Somite 2 tergite 2.3 × broader than long; lateral margins slightly concavely subparallel, posterolaterally blunt. Pleuron of somite 3 laterally blunt. Telson 0.6 × as long as broad, posterior plate slightly longer than anterior plate, posterior margin feebly convex.

Eye: Relatively broad (1.4 × longer than broad), overreaching midlength and falling short of apex of rostrum; lateral and mesial margins somewhat convex. Cornea not dilated, about half length of remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 2.9 × longer than high. Antennal peduncle overreaching eyes. Article 2 with acute distolateral spine. Antennal scale reaching midlength of article 5, slightly broader than that article; lateral margin with small spine at midlength. Article 4 with distinct distomesial spine. Article 5 1.4 × longer than article 4, breadth 0.6 × height of antennular ultimate article. Flagellum consisting of 9 segments, not reaching distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 basis without denticles on mesial ridge. Ischium distolaterally with long setae, crista dentata with very small, obsolescent denticles; flexor margin distally rounded. Merus 1.8 × longer than ischium, flexor margin moderately ridged, somewhat angular at distal third; distolateral spine small. Carpus unarmed.

P1: 5 × longer than carapace, sparingly bearing long soft setae. Ischium dorsally with broad, depressed, lobe-like distal process, ventromesially unarmed. Merus 1.2 × longer than carapace; dorsally smooth, ventrally with a few tuberclelike spines mesial to distal end of ischium. Carpus 1.2 × longer than merus. Palm 3.6 × longer than broad, subequal to length of carpus. Fingers not gaping, somewhat incurved distally, crossing when closed; opposable margin of fixed finger somewhat sinuous, with low eminence medially; movable finger about half as long as palm, opposable margin with low proximal process. P2-4: Moderately compressed mesio-laterally, sparingly with long setae. Meri successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.9 × length of P3 merus), equally broad on P2-4; length-breadth ratio, 3.8-3.9 on P2, 3.5-3.7 on P3, 3.3-3.4 on P4; extensor margin with a few very small spines distinct on proximal half on P2 and P3, obsolete on P4. P2 merus 0.8 × length of carapace, 0.8 × length of P2 propodus; P3 merus 0.8 × length of P3 propodus; P4 merus 0.7 × length of P4 propodus; Carpi successively slightly shorter posteriorly, about one-third length of propodi and 0.6 × length of dactyli on P2-4. Propodi successively slightly shorter posteriorly; flexor margin slightly concave in lateral view, bearing pair of distal spines only. Dactyli slightly shorter on P2 than on P3 and P4, proportionately broad, 3.1-3.4 × longer than broad (breadth measured at base), 1.6 × longer than dactyli and about half as long as propodi on P2-4; flexor margin nearly straight, with 7 or 8 spines obscured by setae, penultimate spine pronouncedly broad and long (5 × broader than ultimate spine), preceded by 5 or 6 slender spines, loosely arranged, moderately inclined and successively diminishing toward base of article, ultimate spine very slender, shorter than antepenultimate.

REMARKS — The present material differs from the holotype (ovigerous female 3.1 mm) in the following: the carapace bears small lateral spines instead of denticle-like spines; the flexor margin of Mxp3 merus is unarmed instead of bearing one or two small spines; and the P2 merus is 0.8 instead of 1.0 times the length of P2 propodus. Molecular analyses would help determine if these are different species.

This species is very similar to U. laurentae n. sp. and U. longicheles Ahyong & Poore, 2004 . Their relationships are discussed under the respective species (see above).

Figures

FIGURE 180 Uroptychus paenultimus Baba, 2005, female 2.3 mm (MNHN-IU-2014-16833). 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, telson.E, left antenna,ventral.F, right Mxp3,lateral.G, left P1, proximal part, setae omitted,ventral.H, same,proximal part omitted,dorsal.Scale bars:1 mm.

FIGURE 181 Uroptychus paenultimus Baba,2005, female 2.3 mm (MNHN-IU-2014-16833). 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. Scale bars:1 mm.