Uroptychus brucei Baba, 1986

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 : 128-130

Uroptychus brucei Baba, 1986

Figure 49

Uroptychus brucei Baba, 1986a: 1 , figs 1, 2. — Ahyong & Poore 2004: 14 (key). — Baba 2005: 219 (key), 225 (synonymy).

TYPE MATERIAL — Holotype: Australia, off Western Australia, 17°59.4’S, 118°18.4’E, 406-416 m, male ( NTM Cr. 000604). [not examined].

MATERIAL EXAMINED — Indonesia, Tanimbar Islands. KARUBAR Stn CC40, 7°46’S, 132°31’E, 443-468 m, 28.X.1991, 1 ♂ 13.7 mm, 1 ♀ 15.8 mm (MNHN-IU-2014-16353).

DISTRIBUTION„ Northwest Australia, and now Tanimbar Islands, Indonesia; 406- 468 m.

DESCRIPTION„ Large species. Carapace: About as long as broad; greatest breadth 1.6 × distance between anterolateral spines. Dorsal surface somewhat granulose and unarmed, slightly convex from anterior to posterior, with moderate depression suggesting cervical groove. Lateral margins with small tubercles or granules; somewhat elevated ridge at end of anterior branchial margin; ridged along posterior third; anterolateral spine well developed, situated posterior to level of but somewhat overreaching much smaller lateral orbital spine, separated from that spine by twice basal breadth. Rostrum sharp triangular, with interior angle of 30°, length less than half that of carapace, breadth less than half carapace breadth measured at posterior carapace margin; dorsal surface concave. Pterygostomian flap finely granulose, anteriorly roundish, with small spine.

Sternum: Excavated sternum anteriorly triangular or ending in small spine, surface with obsolescent ridge in midline. Sternal plastron slightly shorter than broad, lateral extremities gently divergent posteriorly. Sternite 3 strongly depressed, anterior margin excavated in shallow V-shape, with 2 submedian spines flanking deep narrow sinus. Sternite 4 having anterolateral margin smoothly convex, bluntly produced on anterior end, 1.4 × longer than posterolateral margin. Anterolateral margin of sternite 5 strongly convex, about as long as posterolateral margin of sternite 4.

Abdomen: Somite 1 well convex from anterior to posterior, hence transversely ridged. Somite 2 tergite 2.1-2.5 × broader than long; pleuron posterolaterally blunt, lateral margin concavely divergent posteriorly. Pleuron of somite 3 posterolaterally blunt angular. Telson 0.4-0.5 × as long as broad, posterior plate 1.5 × longer than anterior plate, somewhat emarginate on posterior margin.

Eye: Elongate and slender, 2.2-2.6 × longer than broad, slightly overreaching midlength of rostrum, lateral and mesial margins somewhat concave medially. Cornea one-third as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 2.9-3.3 × longer than high. Antennal peduncle distinctly overreaching cornea. Article 2 with small lateral spine. Antennal scale relatively broad, overreaching midlength of, but falling short of distal end of article 5. Article 4 with small distomesial spine. Article 5 2.1-2.5 × longer than article 4, distomesially with distinct spine; breadth 0.6 × height of ultimate antennular article. Flagellum of 43-47 segments overreaching P1 merus.

Mxp: Mxp1 with bases close to each other but not contiguous. Mxp3 basis with 4 or 5 proximally diminishing denticles. Ischium half as long as merus, laterally flattish, mesially excavated longitudinally, flexor margin straight, distally not rounded, crista dentata with 27-30 denticles. Merus 2 × longer than ischium, well ridged along flexor margin, mesial face flattish, with long setae. Carpus unarmed.

P1: Relatively massive, barely setose except for fingers, length 5.1 × (male), 4.8 × (female) that of carapace. Ischium dorsally with strong depressed spine, ventrally with well-developed subterminal spine on mesial margin. Merus tuberculose ventrally and mesially (female), with more pronounced tubercles and small spine about at midlength in line with subterminal spine of ischium (male), length 1.1 × that of carapace. Carpus 1.2-1.3 × longer than merus, somewhat tuberculose ventromesially. Palm 2.3 × longer than broad, subequally long as carpus, ridged moderately along lateral margin, sharply along mesial margin. Fingers distally incurved, crossing when closed, somewhat gaping on proximal three-quarters; movable finger about half as long as palm, opposable margin with 2 processes (1 at middle, 1 at proximal portion) interspersed by a few small processes.

P2-4: Relatively slender, unarmed on merus and carpus. Meri equally broad on P2-4; P2 merus subequal to or very slightly longer than P3 merus as well as carapace, 1.4 × longer than P2 propodus; P3 merus 1.2 × length of P3 propodus; P4 merus 0.8-0.9 × length of P3 merus, subequal to length of P4 propodus; length-breadth ratio, 6.1-6.8 on P2, 5.6-6.5 on P3, 4.6-5.4 on P4. Carpi subequal in length on P2 and P3 or slightly shorter (0.9) on P3 than on P2, P4 carpus 0.9 × length of P3 carpus; carpus-propodus length ratio, 0.6-0.7 on P2, 0.6 on P3, 0.5 on P4; carpus-dactylus length ratio, 1.8 on P2, 1.7 on P3, 1.5 on P4. Propodi subequal in length on P2-4, or slightly shorter on P2 than on P3 and P4; flexor margin ending in pair of spines preceded by row of 11-14 spines on nearly entire to distal two-thirds length on P2, 8-11, 8-9 spines on distal half on P3 and P4 respectively. Dactyli about one-third as long as propodi on P2-4; dactylus-carpus length ratio, 0.6 on P2 and P3, 0.7 on P4; flexor margin well curved, setose, with 9-12 sharp, somewhat inclined, loosely arranged spines subequally broad but somewhat smaller proximally; extensor margin fringed with plumose setae at least on median three-fifths of length.

REMARKS — The ornamentation of the carapace and short dactyli of P2-4 displayed by the species are very much like those of U. brachydactylus Tirmizi, 1964 (see above). However, Uroptychus brucei is readily distinguished from that species by the P1 ischium that bears a well-developed subterminal spine instead of being unarmed on the ventromesial margin; the P2-4 dactyli are not so strongly curved as in U. brachydactylus , bearing a fringe of plumose setae along the extensor margin; and the distal two articles of the antennal peduncle each bear a distinct distomesial spine, instead of being unarmed.

Figures

FIGURE 49 Uroptychus brucei Baba, 1986a, male 13.7 mm (MNHN-IU-2014-16353). A, carapace and anterior part of abdomen, proximal part of right P1 included,dorsal.B, same,lateral.C, sternal plastron,with excavated sternum and basal parts of Mxp1.D, left antenna,ventral.E, right Mxp3,ventral.F, right P1, proximal part,ventral.G, same,dorsal.H, right P2,lateral. I, same,distal part,setae omitted. Scale bars:A, B, F,G, H, 5 mm; C-E,I, 1 mm.