Uroptychus yokoyai, Ahyong & Poore, 2004

Ahyong, Shane T. & Poore, Gary C. B., 2004, The Chirostylidae of southern Australia (Crustacea: Decapoda: Anomura), Zootaxa 436 (1), pp. 1-88 : 79-82

Uroptychus yokoyai n. sp. ( Fig. 25 )

Type material. HOLOTYPE: AM P65827, male (4.0 mm), Gifford Guyot, E of Brisbane, Tasman Sea , 26°44.27’S, 159°28.93’E, 306 m, on Subergorgia coral, beam trawl, FR0589­39, J. Lowry et al. on RV Franklin, 8 May 1989 . PARATYPES: AM P65828, 2 ovigerous females (4.9–5.3 mm), Gifford Guyot, E of Brisbane, Tasman Sea , 26°43.39’S, 159°28.54’E, 295 m, beam trawl, FR0589­38, J. Lowry et al. on RV Franklin, 8 May 1989 .

Diagnosis. Carapace excluding rostrum slightly broader than long; broadest at about midlength; lateral margins convex; with anterolateral spine lateral spine at base of indistinct cervical groove; outer orbital angle produced to distinct spine; dorsum unarmed. Rostrum slightly broader than long. Sternite 3 anterior margin shallowly concave, anterolateral angle obtuse. Eyestalks extending slightly beyond rostrum. Basal antennal segment unarmed; penultimate segment unarmed; ultimate with distal spine. Antennal scale extending beyond midlength but not beyond apex of ultimate peduncle segment. Cheliped propodus, carpus and distal portion of merus with granular ventral surface. Pereopods 2–4 similar; propodi not broadened distally, with 6–8 movable spines on distal flexor margin; dactyli with 8 or 9, obliquely directed spines on flexor margin, distal 3 slender, others quadrate to trapezoid.

Description. Carapace: Breadth slightly greater than length (excluding rostrum); broadest at about midlength. Lateral margins convex, with slender anteriorly directed anterolateral spine lateral spine at base of indistinct cervical groove. Rostrum triangular, slightly broader than long, less than half as long as remaining carapace, apex acute, dorsally distinctly concave. Outer orbital angle produced to distinct spine, extending anteriorly beyond apices of anterolateral spines. Dorsum smooth, unarmed. Pterygostomian flap with small anterior spine.

Sternum: Plastron slightly broader than long. Sternite 3 (at base of maxilliped 3) slightly depressed, anterior margin shallowly concave, anterolateral angle obtuse. Sternite 4 (at base of pereopod 1) with lateral margins anteriorly blunt, extending anteriorly to midlength of emargination of sternite 3.

Abdomen: Segments sparsely setose. Telson four­fifths as long as wide; distal portion trianguloid, apex rounded, about 4 times length of proximal portion.

Eye: Cornea slightly dilated, about half length of peduncle; extending slightly beyond rostrum.

Antenna: Basal segment unarmed. Peduncle extending to apex of rostrum. Flagellum about 3 times as long as peduncle. Ultimate segment 2.5 times as long as penultimate segment; ultimate with distal spine. Antennal scale wider than opposite peduncular segments, extending beyond midlength but not beyond apex of ultimate peduncle segment.

Maxilliped 3: Dactylus and propodus unarmed. Extensor margin of carpus with proximal and distal spinule. Merus with distal spine. Crista dentata serrate for length of ischium, extending onto basis; serrations of basis smaller than that of ischium.

Pereopod 1 (cheliped): Slender, subcylindrical, about 5 times carapace length, sparsely setose; propodus, carpus and distal portion of merus with granular ventral surface. Propodus palm 4 times as long as high, about 2.5 times as long as pollex. Fingers crossing, occlusal margins dentate, with obtuse proximal prominence. Carpus longer than merus and propodal palm. Merus distinctly constricted proximally, inner and outer distal spine. Ischium with slender distolateral spine.

Pereopods 2–4: Sparsely setose, similar, slightly decreasing in length posteriorly. Carpus about 0.5 meral and 0.7 propodal length. Propodi not broadened distally, with 7–9 movable spines on distal flexor margin, distalmost paired. Dactyli with 8 or 9 fixed, obliquely directed spines on flexor margin, distal 3 slender, others quadrate to trapezoid.

Ovum : 1.0 mm diameter.

Etymology. Named for Yu Yokoya, who described the similar species, U. latirostris from Japan; noun in apposition.

Remarks. Although Baba (1988) regarded U. latirostris Yokoya, 1933 as a synonym of U. cavirostris Alcock & Anderson, 1899 , study of the present series of Uroptychus from Australia in combination with published accounts ( Baba 1973, Van Dam 1933) indicates that Yokoya’s species is distinct. Baba (1973) redescribed and illustrated U. latirostris from Japanese material, including topotypes. His account shows that the Japanese form differs from U. cavirostris as figured by Van Dam (1933) in lacking the paired median spines on the anterior margin of sternite 3 and lacks spines on the merus of the third maxilliped. Therefore, we regard U. latirostris as a distinct species and remove it from the synonymy of U. cavirostris .

Uroptychus yokoyai n. sp. most closely resembles U. latirostris , U. cavirostris and U. alcocki n. sp. in the subquadrate carapace with broad, triangular rostrum. Uroptychus yokoyai resembles U. latirostris and differs from U. cavirostris and U. alcocki n. sp. in bearing the broad, U­shaped emargination in sternite 3, without a pair of median spines. The new species further differs from U. cavirostris in having a rounded instead of medially emarginate telson. Uroptychus yokoyai differs from U. latirostris (based on Baba 1973) in bearing a distal spine on the carpus and merus of the third maxilliped, and in bearing numerous tubercles on the ventral surface of propodus and carpus of the chelipeds. According to Yokoya (1933) and Baba (1973), the chelae of U. latirostris are smooth.

Distribution. Known only from the type locality on Subergorgia coral at 295– 306 m.

Figures

FIGURE 25. Uroptychus yokoyai n. sp., holotype male, 4.0 mm, AM P65827. A, dorsum. B, anterior carapace, right lateral. C, cheliped, right ventral. D, cheliped, proximal right lateral. E, sternum. F, telson. G, maxilliped 3, right lateral. H, crista dentata, right. I, antenna, right ventral. Scale A–D = 2 mm, E, G = 1 mm, F, H–I = 0.5 mm.