Uroptychus albus, Mccallum, Anna W. & Poore, Gary C. B., 2013

Mccallum, Anna W. & Poore, Gary C. B., 2013, Chirostylidae of Australia’s western continental margin (Crustacea: Decapoda: Anomura), with the description of five new species, Zootaxa 3664 (2), pp. 149-175 : 156-158

Uroptychus albus sp. nov.

( Fig. 3 )

Type material. Holotype: Female (cl 6.6 mm), Western Australia, off Cape Leveque (14°33.43'S, 121°20.38'E – 14°32.76'S, 121°19.65'E), 924–1101 m, 0 4 July 2007 (stn SS05/2007 156), CSIRO acquisition number 0 19, NMV J56127 .

Diagnosis. Carapace excluding rostrum, slightly longer than wide, with small anterolateral spine; lateral margins convex, broadest at posterior 0.75, irregular but unarmed; dorsum without spines but with scattered scales and rugosities. Rostrum narrow triangular; not extending beyond eyes. Sternite 3 anterior margin deeply concave, with pair of submedian spines separated by tiny notch; anterolateral margin rounded. Eyes with cornea dilated, reaching beyond the rostrum. Second antennal article without outer spine; ultimate and penultimate peduncle articles unarmed. Antennal scale extending just beyond distal end of penultimate peduncle. Maxilliped 3 unarmed. Pereopod 1 slender and smooth, about 3 times carapace length. Pereopod 2 dactylus with 2 close-set distal spines and a few minute median spines oriented parallel to flexor margin; propodus widened on medial flexor margin bearing group of 3 spines and single distal spine.

Description. Carapace: Carapace excluding rostrum 1.05 times as long as broad; width between anterolateral margins 0.6 times that of broadest carapace width at posterior 0.75; lateral margins convex; with rugosities. Rostrum narrow triangular, 1.25 times as long as broad; horizontal; length 0.6 that of remaining carapace. Dorsum with scattered scales and rugosities, without setae. Gastric region with epigastric ridges and low ridge longitudinally, separated from cardiac region by deep depression. Anterolateral spines small. Lateral orbital margin without angle or spine. Pterygostomian flap smooth, anterior margin angular.

Sternum: Sternal plastron 1.5 times broader than long, widening posteriorly. Sternite 3 anterior margin deeply concave, with pair of submedian spines separated by tiny notch; anterolateral margin rounded. Sternite 4 without anterolateral spines or process; surface with a transverse row of tubercles and setae.

Abdomen: Somites glabrous. Telson length about 0.7 breadth; distal portion round (not emarginate), more than twice length of proximal portion.

Eyes: Cornea unpigmented, dilated, longer than length of peduncle. Eyes reaching beyond beyond rostrum.

Antenna: Peduncle extending slightly beyond rostrum. Article 2 without outer spine; ultimate and penultimate articles unarmed; ultimate article 1.7 times length of penultimate article. Antennal scale of similar breadth to article 5, extending just beyond distal end penultimate peduncle.

Maxilliped 3: Dactylus, propodus, carpus and merus unarmed. Crista dentata feebly serrate with 8 denticles; 2 denticles on mesial ridge of basis.

Pereopod 1 (cheliped): Pereopod 1 very slender; about 3.2 times carapace length; sparsely setose. Propodus palm 4.5 times as long as high, 1.5 times as long as pollex. Fingers not crossing distally, occlusal margins finely dentate with single low process on base of pollex. Carpus 1.3 times longer than merus and 1.3 times propodal palm; with a few setae. Merus and ischium smooth on inner proximal margin; ischium unarmed.

Pereopod 2: Merus and carpus unarmed and with sparse setae. Carpus 0.6 merus length, 0.8 propodus length. Propodus with long setae distally, broadened medially, with flexor margin straight on proximal third, distal twothirds subprehensile with dactylus flexor margin and densely setose, bearing a group of 3 slender blunt robust spines at midpoint and 1 distal robust spine. Dactylus strongly curved, flexor margin with 3 minute median spines oriented parallel to margin and distally with 2 close-set spines. Pereopods 3 and 4 missing.

Etymology. From the Latin albus meaning ‘white’ in reference to the unpigmented eyes.

Distribution. North-western Australia, off Cape Leveque, 924–1101 m.

Remarks. Although Uroptychus albus bears minute spines on the flexor margin of the dactylus, only the two distal spines are robust and distinct, a character shared with U. bispinatus Baba, 1988 , U. thermalis Baba & de Saint Laurent, 1992, U. pilosus Baba, 1981 and U. sternospinosus Tirmizi, 1966 , all found in environments deeper than 900 m. These species are also similar to U. albus as they possess a short antennal scale (only reaching or slightly overreaching the distal end of the penultimate antennal article), and a distinct dorsal depression between the cardiac and gastric regions. The new species has a short rostrum which does not extend beyond the eyes which distinguish it from U. bispinatus and U. pilosus in which the rostrum always overreaches the eyes. Furthermore, the carapace dorsum of U. albus is rugose with scattered scales and lacks setae, whereas U. bispinatus has a smooth carapace dorsum and U. pilosus is covered in fine setae across the carapace and abdomen. Uroptychus albus can be distinguished from U. sternospinosus which bears a pair of spines on the epigastric region and large lateral spines on sternite 3. The carapace dorsal surface of U. albus is most similar to that of U. thermalis , both being rugose with scattered scales. These two species can be distinguished by the distal spines of the dactyli, which are well separated in U. thermalis and almost touching in U. albus ; the pereopod 2 carpus which is subequal in length to the dactylus in U. thermalis and distinctly shorter in U. albus ; and also by the length of the rostrum which does not reach beyond the eyes in U. albus .

Figures

FIGURE 3. Uroptychus albus sp. nov., female (6.6 mm), NMV J 56127. A, carapace and abdomen, dorsal. B, carapace, lateral. C, sternum. D, telson. E, left antenna, ventral. F, maxilliped 3, basis and ischium, right, ventral. G, pereopod 1, right. H, pereopod 2. Scales = 1 mm.