Uroptychus patulus, 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 : 69-71

Uroptychus patulus nov. ( Fig. 20 )

Type material. HOLOTYPE: NMV J21045 , 1 ovigerous female (12.3 mm), 80 km SSW of Point Hicks, Bass Strait , Victoria, 38°20.91’S, 149°38.33’E, 1030 m, engels high­lift trawl, M. Norman, 14 May 1988 . PARATYPES: SAM C6065 , 1 ovigerous female (12.6 mm), 76 km SSE of Southeast Cape , Tasmania, 44°12.0–12.1’S, 147°20.1–20.5’E, 955– 1190 m, FV Corvina, K. Gowlett­Holmes , 8 Feb 1992 ; SAM C6063 , 10 males (7.4–12.7 mm), 9 females (8.0– 15.1 mm), 7.3 km SSE of Southeast Cape , Tasmania, 41°15.8’S, 147°05.3’E, 970–1190 m, trawled, FV Belinda, K. Gowlett­Holmes , 7 Feb 1992 .

Diagnosis. Carapace excluding rostrum distinctly broader than long; lateral margins smooth, distinctly convex, broadest posterior to midlength; with distinct, slightly incurved anterolateral spine; outer orbital angle rounded, unarmed; dorsum unarmed. Rostrum sharply triangular. Sternite 3 anterior margin with deep V­shaped emargination; outer lobes of emargination obtusely angled. Basal antennal segment without outer spine; ultimate and penultimate segments unarmed. Antennal scale extending about to midlength of ultimate peduncle segment. Cheliped about twice carapace length; propodus palm slightly less than twice as long as dactylus. Pereopods 2–4 similar, propodi not broadened distally, unarmed; dactyli lined with 20–30 small triangular teeth on flexor margin.

Description. Carapace: Breadth greater than length (excluding rostrum). Lateral margins smooth, distinctly convex, broadest posterior to midlength; with distinct, slightly incurved anterolateral spine; posterior fifth with low, indistinct ridge. Rostrum sharply triangular, about half length of remaining carapace, margins unarmed. Outer orbital angle rounded, unarmed. Dorsum minutely punctate, finely but sparsely­setose, unarmed. Pterygostomian flap without anterior spine.

Sternum: Plastron broader than long, slightly widening posteriorly. Sternite 3 (at base of maxilliped 3) not depressed, anterior margin with deep V­shaped emargination; outer lobes of emargination obtusely angled. Sternite 4 (at base of pereopod 1) with obtuse anterolateral margin, extending anteriorly to about midlength of emargination of sternite 3.

Abdomen: Segments glabrous. Telson about half as long as broad; distal portion posteriorly emarginate, about 1.5 times length of proximal portion.

Eye: Cornea not dilated, about one­third length of peduncle; not reaching to proximal half of rostrum.

Antenna: Basal segment without outer spine. Peduncle extending to distal third of rostrum. Flagellum about 1.5 times as long as peduncle. Ultimate and penultimate segments unarmed; ultimate segment about 1.5 times length of penultimate segment. Antennal scale wider than opposite peduncular segments, extending about to midlength of ultimate peduncle segment.

Maxilliped 3: Dactylus, propodus, carpus and merus unarmed. Crista dentata distinctly serrate on proximal half of ischium, not extending onto basis.

Pereopod 1 (cheliped): Slender, subcylindrical; about twice carapace length; setose. Propodus with palm less than three times as long as high, slightly less than twice as long as dactylus; lower distal margin straight to slightly concave. Fingers crossing, occlusal margins finely dentate; occlusal margin of dactylus with obtuse process proximally; occlusal margin of pollex with low prominence distal to midlength. Carpus longer than merus and as long as propodal palm; setose. Merus and ischium without tubercles on inner proximal margin; ischium with low triangular projection on outer margin.

Pereopods 2–4: Setose, similar, becoming shorter distally; propodi, carpi and meri unarmed. Carpus of pereopods 2–3 about half merus and propodus length. Carpus of pereopod 4 about 0.6 merus length, about 0.4 propodus length. Propodi not broadened distally, unarmed. Dactyli lined with 20–30 fixed, small triangular teeth on flexor margin, but obscured by setae.

Ovum : 2.0 mm diameter.

Etymology. Named patulus , from the Latin meaning ‘broad’, alluding to the broad carapace of the species.

Remarks. Uroptychus patulus n. sp. closely resembles U. longvae n.sp., U. onychodactylus Tirmizi, 1964 from the Maldives and U. setosidigitalis Baba, 1977b from Midway Island in the broad carapace, broad V­shaped anterior emargination of sternite 3, and elongate, curved, minutely toothed dactyli of pereopods 2–4. Differences between U. patulus and U. longvae are outined under the account of the latter. Uroptychus patulus differs from U. onychodactylus and U. setosidigitalis having a rounded instead of pointed outer orbital margin. Uroptychus patulus further differs from U. setosidigitalis in lacking an outer spine on the basal antennal segment and in lacking the dense covering of fine setae on the pereopods.

Of the Australian species, U. patulus also resembles U. laperousazi n. sp. and U. latus n. sp. in the in the short, broad, carapace and broad V­shaped anterior sternal emargination. Uroptychus patulus differs from both U. laperousazi and U. latus in having short, triangular teeth instead of well spaced, upright spines on the flexor margins of the dactyli of pereopods 2–4.

Distribution. Eastern Bass Strait and off southeastern Tasmania at 955–1190 m.

Figures

FIGURE 20. Uroptychus patulus n. sp., holotype female, 12.3 mm, NMV J21045. A, dorsum. B, anterior carapace, right lateral. C, telson. D, sternum. E, maxilliped 3, right lateral. F, crista dentata, right. G, antenna, right ventral. A–B = 2 mm, C–E = 1 mm, F–G = 0.5 mm.