Uroptychus rafai, Baba, Keiji & Wicksten, Mary K., 2017

Baba, Keiji & Wicksten, Mary K., 2017, Uroptychus nitidus (A. Milne-Edwards, 1880) and related species (Crustacea: Decapoda: Anomura: Chirostylidae) from the western Atlantic, Zootaxa 4221 (3), pp. 251-290 : 274-277

Uroptychus rafai n. sp.

( Figs. 15 , 16 )

Type material. Holotype: USNM 1107844 , male (CL 8.3), Straits of Florida, 23°51’N, 81°02’W, 1107–1162 m, 16 Sept. 1964.

Description. Carapace: 1.2 × longer than broad; greatest breadth 1.7 × distance between anterolateral spines. Dorsal surface smooth and glabrous, moderately convex from anterior to posterior, with shallow depression between gastric and cardiac regions. Lateral margins weakly convex and weakly divergent posteriorly, with row of short oblique ridges (obscurely denticulate in dorsal view), distinctly ridged along posterior third. Anterolateral spine directed straight forward, overreaching lateral orbital spine. Rostrum narrow triangular, with interior angle of 24°, directed slightly ventrally, dorsal surface somewhat concave, length 1.2 × breadth and 0.4 × that of remaining carapace, breadth slightly less than half that of carapace measured at posterior margin. Lateral limit of orbit angular, ending in small spine posterolaterally obliquely leading to anterolateral spine. Pterygostomian flap anteriorly roundish, ending in tiny spine.

Sternum: Excavated sternum with spiniform anterior margin between close bases of Mxp1; surface with small spine in center. Sternal plastron as long as broad; lateral extremities posteriorly divergent between sternites 3 and 6, subparallel between sternites 6 and 7. Sternite 3 moderately depressed, anterior margin deeply excavated, with 2 submedian spines separated by V-shaped notch. Sternite 4 anterolateral margin convex, anteriorly ending in short spine not reaching anterior end of sternite 3, followed by 3 proximally diminishing obtuse spines, length 1.3 × longer than posterolateral margin. Anterolateral margin of sternite 5 as long as posterolateral margin of sternite 4.

Abdomen: Smooth and glabrous. Somite 1 weakly convex from anterior to posterior. Somite 2 tergite 2.4 × broader than long, pleuron weakly divergent posteriorly, posterolateral margin rounded, not tapering. Pleura of somites 3–4 ending in blunt margin. Telson half as long as broad; posterior lobe 1.5 × longer than anterior lobe, weakly emarginate on posterior margin.

Eyes: 1.5 × as long as broad, reaching distal fifth point of rostrum. Cornea slightly broader than, and as long as remaining ocular peduncle.

Antennule and antenna: Ultimate article of antennule 3.1 × longer than broad. Antennal peduncle slightly overreaching eye, barely reaching rostral tip. Article 2 with sharp distolateral spine. Antennal scale tapering, terminating in midlength of article 5, breadth less than 1.6 × that of article 5. Articles 4 and 5 unarmed; article 5 1.6 × longer than article 4, breadth one-third height of ultimate antennular article. Flagellum of 14 segment not reaching end of P1 merus.

Mxp: Mxp1 with bases close to each other. Mxp3 basis with 3 or 4 denticles on mesial ridge. Ischium having flexor distal margin not rounded, crista dentata with more than 30 denticles decreasing toward distal end. Merus and carpus unarmed; merus 2.5 × longer than ischium, flexor margin moderately roundly ridged.

P1: 5.1 × longer than carapace, glabrous on merus and palm, sparsely setose on carpus, densely so on fingers. Ischium with very small dorsal spine, unarmed on ventromesial margin. Merus 1.3 × longer than carapace, ventrally with granulate short ridges. Carpus subcylindrical, 1.3 × longer than merus. Palm 3.1 × longer than broad, ventrally feebly granulose, with blunt mesial and lateral spines distally; length 0.8 × that of carpus. Fingers gaping in proximal half, each distally ending in small incurved spine; fixed finger medially obtusely produced at midlength on opposable margin; movable finger with broad truncate, bicuspid process at midlength of gaping opposable margin, length 0.6 that of palm.

P2–4: Slender, moderately compressed, with setae sparse on meri and carpi, numerous on propodi and dactyli, those on carpi and propodi long, more than length of dactylus. Meri unarmed, successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.7 × length of P3 merus); length-breadth ratio, 7.6 on P2, 6.1 on P3, 4.9 on P4; P2 merus as long as carapace, 1.4 × length of P2 propodus, P3 merus 1.2 × length of P3 propodus, P4 merus 0.9 × length of P4 propodus. Carpi unarmed, successively shorter posteriorly; carpus-propodus length ratio, 0.6 on P2 and P3, 0.5 on P4. Propodi subequal in length; flexor margin straight, with 9, 8, 6 basally articulated spines on P2, P3 and P4 respectively, distal-most single, more remote from distal end of margin than from distal second spine. Dactyli subequal, 0.4 × length of propodus; flexor margin curving at proximal third, with 9 or 10 moderately obliquely directed, proximally diminishing subtriangular spines, ultimate spine slightly larger than penultimate.

Remarks. The distalmost of the flexor marginal spines of P2–4 propodi is single in U. rafai and U. fenneri n. sp. unlike those of the other species that have a pair of spines. Uroptychus rafai is distinguished from U. fenneri by the carapace without a pair of epigastric processes or ridges, the antennal scale never reaching instead of extending beyond the distal end of article 5, and the terminal flexor marginal spine of P2–4 propodi more remote from the juncture with the dactylus than from the distal second spine. In addition, the Mxp3 crista dentata bears more numerous denticles (30 versus 13–17), P2 relatively is more slender (the length-breadth ratio, 7.6 versus 4.9–5.9), and the P2–4 dactylar spines are more obliquely directed.

Distribution. Known from the type locality only.

Etymology. Named for Rafael Lemaitre for arranging funds for KB to visit the Smithsonian Institution in 2007 and for all of his help rendered to KB during his stay there.

Figures

FIGURE 15. Uroptychus rafai n. sp., male (CL 8.3), holotype, USNM 1107844. A, carapace and anterior part of abdomen, dorsal. B, same, lateral. C, sternal plastron, with excavated sternum, proximal part of Mxp 1 included. D, telson. E, left antenna, ventral. F, right Mxp 3, ventral. Scales = 1 mm.

FIGURE 16. Uroptychus rafai n. sp., male (CL 8.3), holotype, USNM 1107844. A, left P 1, dorsal. B, same, ischium and merus, ventral. C, same, fingers, ventral. D, right P 2, lateral. E, same, distal part, setae omitted, lateral. F, right P 3, lateral. G, right P 4, lateral. Scales = 5 mm for A – C; 1 mm for D – G.