Uroptychus alcocki, 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 : 15-18

Uroptychus alcocki n. sp. ( Fig. 2 )

Type material. HOLOTYPE: AM P31412, female (9.0 mm), SE of Ballina , New South Wales, 29°02’S, 153°48’E, 137 m, K78­23­02, 1 Nov 1978 . PARATYPES: AM P65834, 1 female (8.0 mm), type locality ; AM P31411, 2 males (5.3–6.2 mm), 2 females (4.8–6.7 mm), E of Capricorn Group , Queensland, 23°19.5’S, 152°35.4’E, 320 m, HMAS Kimbla, Stn 23, W. Ponder et al., 14 Dec 1977 ; AM P65836, 13 males (3.5–8.8 mm), 2 ovigerous females (7.9–8.0 mm), Britannia Seamount, E of Brisbane, Tasman Sea , 28°17.47’S, 158°37.89’E, 419 m, limestone and coarse coral sand, benthic sled, FR0589­47, J. Lowry et al. on RV Franklin , 10 May 1989 ; AM P65835, 1 ovigerous female (8.9 mm), E of Port Stephens , New South Wales, 32°54’S, 152°34’E, 150 m, K78­26­08, 6 Dec 1978 .

Diagnosis. Carapace, excluding rostrum, slightly longer than broad; lateral margins with anterolateral spine, lateral spine at base of indistinct cervical groove and usually with small spine anterior to midlength of lateral margin; dorsum unarmed. Rostrum slightly broader than long. Sternite 3 anterior margin distinctly but shallowly concave with pair of median spines. Eyes not extending beyond rostrum. Basal antennal segment with small outer spine; ultimate segment with distal spine. Antennal scale slightly extending beyond midlength but not beyond apex of ultimate peduncle segment. Cheliped propodus palm entirely granular; carpus, merus and ischium with distinctly granular ventral surface.

Description. Carapace: Lateral margins subparallel, with slender anteriorly directed anterolateral spine, lateral spine at base of indistinct cervical groove and usually with small spine anterior to midlength of lateral margin. Rostrum triangular, slightly broader than long, slightly longer than half the remaining carapace length, apex acute, dorsally distinctly concave. Outer orbital angle produced to small spine, extending anteriorly beyond apices of anterolateral spines. Dorsum smooth, unarmed. Pterygostomian flap with small anterior spine.

Sternum: Plastron about as broad as long. Sternite 3 (at base of maxilliped 3) slightly depressed, anterior margin distinctly but shallowly concave with pair of median spines, anterolateral angle obtuse, irregular. Sternite 4 (at base of pereopod 1) with lateral margins anteriorly blunt, extending anteriorly to base of median spines of sternite 3.

Abdomen: Segments sparsely setose. Telson wider than long; distal portion rounded to trianguloid with rounded apex, length varying from half to two­thirds width.

Eye: Cornea slightly dilated, about half­length of peduncle, not extending beyond rostrum.

Antenna: Basal segment with small outer spine. Peduncle not extending to apex of rostrum. Flagellum about 2.5 times peduncle length. Ultimate segment 2.5 times as long as penultimate segment; with distal spine. Antennal scale slightly wider than opposite peduncular segments.

Maxilliped 3: Dactylus and propodus unarmed. Carpus with proximal and distal spinule of extensor margin. Merus with distal extensor marginal spine. Crista dentata serrate for length of ischium, extending onto basis; basis similarly serrate.

Pereopod 1 (cheliped): Slender, subcylindrical, about 4 times carapace length, sparsely setose; propodus palm entirely granular; carpus, merus and ischium with distinctly granular ventral surface. Propodus palm 4 times as long as high, about 2 times as long as pollex. Fingers crossing, occlusal margins dentate, with obtuse proximal prominence; dactylus sparsely granular proximally. Carpus longer than merus and propodal palm, with distinct distodorsal tubercle or denticle. Merus without distinct proximal constriction, with small inner distal spine. Ischium with slender distolateral spine.

Pereopods 2–4: Sparsely setose, similar, slightly decreasing in length posteriorly. Propodi not broadened distally, with 6–10 movable spines on distal flexor margin, distalmost paired. Dactyli with 7–9 fixed, obliquely directed, spines on flexor margin, all slender. Pereopods 2–3 carpus about 0.5 merus and 0.6 propodus length. Pereopod 4 carpus 0.6 merus and propodus length.

Ovum : 1.0– 1.1 mm diameter.

Etymology. Named after the late A. Alcock, who described the similar species, U. cavirostris , and who has made invaluable contributions to the study of the fauna of the Andaman Sea.

Remarks. Uroptychus alcocki n. sp. closely resembles U. cavirostris Alcock, 1899 from the Andaman Sea, U. latirostris Yokoya, 1933 from Japan, and U. yokoyai n. sp. from eastern Australia in the subquadrate carapace and broad, triangular rostrum.

Uroptychus alcocki and U. cavirostris are distinguished from U. latirostris and U. yokoyai by the presence of a pair of median spines on the anterior margin of the median concavity of sternite 3.

Uroptychus alcocki is distinguished from U. cavirostris by the posteriorly rounded instead of medially emarginate telson and presence of distinct granulation on the propodus and ventral surfaces of the carpus, merus and ischium of the cheliped. According to Alcock (1899), the surfaces of the chelipeds of U. cavirostris are smooth aside from “a few squamous granules on the underside of the base of the merus” (p. 27) and the distal spinule or denticles on the propodus and carpus.

Specimens of U. alcocki smaller than 6.7 mm cl. have sparse upper granulation on the propodus of the chelae; larger specimens have densely granulate chelae. Thus, the distinction between U. alcocki and U. cavirostris in cheliped granulation is not a mere artefact of size because Alcock’s holotype of U. cavirostris has a carapace length of about 8.3 mm.

The discovery of two new species similar to U. cavirostris and the recognition of U. latirostris (see Remarks under account of U. yokoyai n. sp.), suggests that published records of U. cavirostris outside the Andaman Sea type locality require verification. Van Dam’s (1933) records of U. cavirostris from Indonesia could be referable to U. alcocki . Tirmizi’s (1964) U. cavirostris from the Maldives do not conform well to the type description and figure. In particular, the rostrum as figured by Tirmizi (1964: fig. 34) appears to be too narrow, the chelae are relatively short, and the lateral spine on the carapace is small and hardly projects from the margin. Tirmizi’s (1964) specimens are probably misidentified and could be small specimens of U. longioculus Baba, 1990 (described from Madagascar), in which the lateral carapace spines are yet to be fully developed.

Distribution. Off central Queensland and northern New South Wales at 140– 320 m.

Figures

FIGURE 2. Uroptychus alcocki n. sp., female holotype, 9.0 mm, AM P31412. A, dorsum. B, anterior carapace, right lateral. C, cheliped, right ventral. D, sternum. E, telson. F, maxilliped 3, right lateral. G, crista dentata, right. H, antenna, right ventral. Scale A–C = 3 mm, D = 1.5 mm, E–H = 0.8 mm.