Uroptychus reedae, 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 : 277-281

Uroptychus reedae n. sp.

( Figs. 17–19 )

Diptychus nitidus . — A. Milne-Edwards, 1880: 62 (part). Uroptychus uncifer . — Chace 1942: 20 (part).

Type material. Holotype: MCZ CRU- 2830, 1 male (CL 4.0), St. Christopher & Nevis, off St. Kitts, 17°19´27”N, 62°50´30”W, 250 fms [457 m], 14 Jan. 1879, Blake Sta. 147.

Paratypes: MCZ CRU- 2623, 1 male (CL 5.9), off Grenada, 11° 27’0”N, 62° 11’0”W, 164 fms [300 m], 27 Feb. 1879, Blake Sta. 254 . MCZ CRU- 2638, 1 male (CL 3.2), off Carriacou , 12°28’22”N, 61°32’18”W, 163 fms [298 m], 24 Feb. 1879, Blake Sta. 241 . MCZ CRU- 2845, 1 male (CL 4.4), off Barbados, 13°3’55”N, 59°38’25”W, 106 fms [194 m], 5 Mar. 1879, Blake Sta. 277.

Description. Carapace: As long as or [very slightly (at most 1.1 ×) longer than] broad; greatest breadth [1.5]– 1.7 × distance between anterolateral spines. Dorsal surface smooth, glabrous and unarmed, somewhat convex from anterior to posterior in profile, with feeble depression between gastric and cardiac regions. Lateral margins obscurely denticulate, divergent posteriorly, slightly convex around branchial region, distinctly ridged along posterior third. Anterolateral spine well developed, directed anteriorly, situated [directly lateral to] or very slightly posterior to small lateral orbital spine, overreaching that spine. Rostrum 0.8–[0.9] × as long as broad, relatively broad at base, narrow distally, with interior angle of [20]–25°, straight horizontal, slightly overreaching eye; length [0.4] × (rarely 0.3 ×) that of remaining carapace, breadth two-thirds that of carapace measured at posterior margin; lateral margins medially concave; dorsal surface concave. Pterygostomian flap anteriorly produced to distinct spine.

Sternum: Excavated sternum sharply produced anteriorly, surface with small spine in center. Sternal plastron about as long as broad, sternites 4–7 successively slightly broader posteriorly. Sternite 3 deeply depressed, anterior margin V-shaped or semicircular, with pair of submedian spines, laterally angular, anterolateral end with distinct low spine. Sternite 4 anterolateral margin somewhat convex and irregular, anteriorly ending in stout spine slightly overreaching lateral base of submedian spines of sternite 3, followed by [a few small] or obsolescent spines, length 2.0 × that of posterolateral margin. Sternite 5 with anterolateral margins 1.8 × longer than posterolateral margin of sternite 4.

Abdomen: Tergites smooth and glabrous. Somite 1 gently convex from anterior to posterior, not transversely ridged. Somite 2 tergite [2.3]–2.8 × broader than long; pleuron posterolaterally with rounded terminus, lateral margins somewhat concavely divergent posteriorly. Pleura of somites 3 and 4 laterally blunt. Telson 0.4–[0.5] × as long as broad; posterior plate distinctly emarginate on posterior margin, length 1.5–[1.6] × that of anterior plate.

Eye: Short relative to breadth (1.4–1.8 [1.5] × longer than broad), slightly falling short of apex of rostrum. Cornea very slightly or barely dilated, length slightly more than half that of remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle [2.5]–3.0 × longer than high. Antennal peduncle slightly overreaching cornea. Article 2 with short, stout distolateral spine. Antennal scale relatively slender, about as broad as article 5, slightly falling short of distal end of that article. Articles 4 unarmed. Article 5 distomesially unarmed or roundly produced and not spiniform, length [2.0]–2.2 × that of article 4, breadth [0.4]– 0.5 × height of ultimate antennular article. Flagellum of 15 segments [reaching] or slightly overreaching distal end of P1 merus.

Mxp: Mxp1 with bases very close and nearly contiguous to each other. Mxp3 unarmed on merus and carpus. Basis with 4 denticles on mesial ridge. Ischium with 20–[25] denticles on crista dentata, flexor margin not rounded distally. Merus about twice as long as ischium, relatively thick mesio-laterally, flexor margin sharply ridged.

P1: Massive (greatest breadth measured on palm subequal to distance between lateral orbital spines of carapace), distally setose, sparsely so elsewhere; length 4.5–[5.2] × that of carapace. Ischium with sharp dorsal spine, unarmed elsewhere. Merus [1.1]–1.2 × longer than carapace, ventrally with obsolescent distomesial and distolateral spines, and sparsely granulate on ventro-proximal portion. Carpus 1.0–[1.2] × longer than merus, subcylindrical or slightly depressed dorsoventrally (height 0.9 × breadth), ventrally spineless. Palm depressed (height 0.6–0.8 [0.7] × breadth), 2.2–2.6 [2.3] × longer than broad, slightly shorter [0.9 ×] or slightly longer (1.1 ×) than carpus, mesial margin smooth and roundly ridged, ventral surface polished. Fingers gaping or not gaping, not distinctly crossing distally, each ending in slightly incurved tip; opposable margins straight and meeting in minutely dentate distal third when gaping, in distal two-thirds when not gaping, that of movable finger with [weakly bicuspid] or obtuse proximal process. Movable finger 0.6–[0.7] × as long as palm.

P2–4: Slender, sparsely setose, propodi with longer setae. Meri successively shorter posteriorly (P3 merus [0.9]–1.0 × length of P2 merus, P4 merus 0.8 × length of P3 merus); length-breadth ratio, 4.9–5.9 [5.5] on P2, 4.6– 4.8 [4.8] on P3, 4.0 on P4; dorsal and ventrolateral margins unarmed; P2 merus 0.9 × as long as carapace, 1.2–1.3 [1.2] × length of P2 propodus; P3 merus 0.9–1.1 [1.0] × length of P3 propodus; P4 merus 0.8 × length of P4 propodus. Carpi subequal on P2–4; carpus-propodus length ratio, [0.5]–0.6 on P2, 0.5 on P3, 0.4 on P4. Propodi subequal on P2 and P3, shorter on P2; flexor margin nearly straight, with pair of terminal spines preceded by row of [6]–9 basally articulated, long spines on P2, [5]–7 spines on P3, 4 spines on P4. Dactyli subequal on P2–4, gently curving at proximal third, length 0.4 × that of propodus on P2–4; dactylus-carpus length ratio, 0.7–[0.8] on P2, 0.8 on P3, 0.9 on P4; flexor margin with [8]–10 subtriangular, moderately obliquely directed spines, distal 3 or 4 subequal in breadth.

Remarks. Females have not been collected. The new species is so similar to U. uncifer ( A. Milne-Edwards, 1880) that Chace (1942) overlooked differences between U. uncifer and U. reedae n. sp. The syntypes of U. nitidus from Blake Stations 147, 241, 254, 277 and 297 that were referred to U. uncifer by Chace (1942) actually represent a different species described above as U. reedae n. sp. Uroptychus reedae is distinguished from U. uncifer by the P1 ischium, which is unarmed instead of bearing a well-developed subterminal spine on the ventromesial margin, and by the antennal peduncle, which is unarmed instead of bearing a distinct distomesial spine on each of articles 4 and 5.

Distribution. Off St. Kitts, Carriacou, Barbados and Grenada, 194– 457 m.

Etymology. Named for Karen Reed for her help during a visit of KB to the Smithsonian Institution in 2007.

Figures

FIGURE 17. Uroptychus reedae n. sp., holotype, male (CL 4.0), MCZ CRU- 2830. 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, right antenna, ventral. F, right Mxp 3, ventral; G, same, lateral. Scales = 1 mm.

FIGURE 18. Uroptychus reedae n. sp., holotype, male (CL 4.0), MCZ CRU- 2830, left P 1. A, ischium and merus, dorsal. B, same, ventral. C, carpus, palm and fingers, dorsal. D, same, mesial. Scale = 1 mm.

FIGURE 19. Uroptychus reedae n. sp., holotype, male (CL 4.0), MCZ CRU- 2830. A, left P 2, lateral. B, same, distal part, setae omitted, lateral. C, left P 3, setae omitted, lateral. D, same, distal part, lateral. E, left P 4, lateral. F, same, distal part, lateral. Scales = 1 mm.