Uroptychus belos, 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 : 25-27

Uroptychus belos n. sp. ( Fig. 5 )

Type material. HOLOTYPE: AM P65830, female (5.4 mm), Britannia Seamount, SE 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 . PARATYPE: AM P65831, 1 male (5.3 mm), type locality .

Diagnosis. Carapace excluding rostrum broader than long; lateral margins with stout anteriorly directed anterolateral spine and 4 strong lateral spines; dorsum glabrous. Rostrum elongate, exceeding half remaining carapace length. Sternite 3 anterior margin shallowly concave, with U­shaped median notch. Basal antennal segment with distinct outer spine; ultimate and penultimate segments with distal spine. Antennal scale extending almost to apex of ultimate peduncle segment. Pereopods 2–4 similar; propodi not broadened distally, with movable spine on distal flexor margin; dactyli with 7 or 8 well­spaced, obliquely directed, corneous teeth on flexor margin, penultimate distinctly larger and broader than others, ultimate spiniform.

Description. Carapace: Breadth greater than length (excluding rostrum); broadest at about midlength. Lateral margins slightly convex, with stout anteriorly directed anterolateral spine and 4 strong lateral spines. Rostrum elongate, exceeding half remaining carapace length, apex acute, margins straight, slightly concave dorsally. Outer orbital angle produced to distinct spine, shorter than anterolateral spines. Dorsum glabrous, unarmed. Pterygostomian flap with anterior spine; lateral surface smooth.

Sternum: Plastron as long as broad. Sternite 3 (at base of maxilliped 3) slightly depressed, anterior margin shallowly concave, with U­shaped median notch, anterolateral angle obtuse, unarmed laterally. Sternite 4 (at base of pereopod 1) with lateral margins produced, angular, extending anteriorly to base of median notch of sternite 3.

Abdomen: Segments sparsely setose, otherwise glabrous. Telson about twice as wide as long; distal portion faintly emarginate, about 1.5 times length of proximal portion.

Eye: Cornea not dilated, about half length of peduncle; extending to distal quarter of rostrum.

Antenna: Basal segment with distinct outer spine. Peduncle almost extending to apex of rostrum. Flagellum almost twice as long as peduncle. Ultimate segment longer than penultimate segment; both segments with distal spine. Antennal scale wider than opposite peduncular segments, extending almost to apex of ultimate peduncle segment

Maxilliped 3: Dactylus, propodus and carpus unarmed. Merus with distal extensor and 2 small flexor marginal spines. Crista dentata denticulate for almost entire length of ischium, not extending onto basis.

Pereopod 1 (cheliped): Slender, subcylindrical, sparsely setose, about 3 times carapace length. Propodus palm 4 times as long as high, about 2.5 times as long as pollex. Fingers crossing, occlusal margins dentate, irregular; dactylus with blunt tooth slightly proximal to midlength. Carpus longer than merus, slightly shorter than propodal palm. Ischium with small distolateral spine.

Pereopods 2–4: Sparsely setose, similar, slightly decreasing in length posteriorly. Propodi not strongly broadened distally, with pair of movable spines on distal flexor margin. Dactyli with 7 or 8 fixed, well­spaced, obliquely directed, corneous teeth on flexor margin, penultimate distinctly larger and broader than others, ultimate spiniform. Pereopods 2–3 carpus about 0.4 merus and propodus length. Pereopod 4 carpus about 0.5 merus length, about 0.3 propodus length.

Etymology. Named belos, Greek , meaning dart or arrow, in reference to the sharp lateral spines on the carapace.

Remarks. Uroptychus belos n. sp. resembles U. crassipes from Indonesia in the shape and spination of the carapace, elongate eyestalks and the shape of the anterior sternites. Uroptychus belos resembles U. longicheles n. sp. in the general carapace shape, elongate eyestalks, slender chelipeds, armature of the dactyli of the walking legs and sternal morphology. Uroptychus belos differs from U. longicheles in the following features: the rostrum has straight instead of concave margins with a sharp instead of rounded apex; the lateral carapace spines are much larger and more robust; the anterolateral carapace spine overreaches the outer orbital spine; the distal segment of the antennal peduncle is armed distally; the antennal scale is nearly as long as instead of markedly shorter than the peduncle; the branchiostegal surface lacks a field of spinules; and the penultimate spine of the flexor margin of the dactyli of the walking legs is broad and blunt instead of triangular. In the lateral spination of the carapace, U. belos also resembles U. crassipes Van Dam, 1939 , from Indonesia, but is readily distinguished by its singular instead of trifid rostrum, the slender and sparsely glabrous instead robust, rugose and strongly setose cheliped, absence of a distal ventral spine on the merus of the walking legs and in having 6–8 instead 10–16 spines on the flexor margins of the dactyli of the walking legs.

Distribution. Presently known only from the type locality.

Figures

FIGURE 5. Uroptychus belos n. sp., holotype female, 5.4 mm, AM P65830. A, dorsum. B, anterior carapace, right lateral. C, cheliped merus, proximal left lateral. D, telson. E, sternum. F, maxilliped 3, right lateral. G, crista dentata, right. H, antenna, right ventral. Scale A–C = 2 mm, D–F, H = 1 mm, G = 0.5 mm.