Uroptychus empheres Ahyong & Poore 2004, n. sp.

Uroptychus empheres n. sp. (Fig. 8)

Uroptychus australis.– Poore, Hart, Taylor & Tudge, 1998: 69 [part, not U. australis (Henderson, 1885)].

Type material. HOLOTYPE: NMV J52864, male (14.4 mm), “Andys” Seamount, Tasmania, 65.5 km SSE of SE Cape, 44°10.8’S, 147°00.0’E, 800 m, epibenthic sled, SS01/97/56, T. Stranks et al., 29 Jan 1997. PARATYPES: NMV J52863, 3 males (14.1–16.5), 8 females (10.4–14.2 mm), type locality.

Diagnosis. Carapace excluding rostrum distinctly longer than broad; irregularly tuberculate behind base of cervical groove; without posterolateral ridge; anterolateral spine small. Rostrum sharply triangular. Outer orbital spine extending to level of anterolateral spine. Dorsum smooth, occasionally with pair of low epigastric scales. Sternite 3 strongly depressed, anterior margin narrow, deeply emarginate, with pair of median spines. Sternite 4 surface granulate. Basal antennal segment with lateral spine. Ultimate and penultimate segments of antennal peduncle unarmed; ultimate segment slightly exceeding twice length of penultimate segment. Antennal scale slightly shorter than to slightly longer than ultimate peduncle segment. Cheliped with inner and ventral margin of propodal palm, carpus and merus granular. Pereopod 2–4 propodus with distalmost movable flexor spines paired; dactyli with 7–10 obliquely directed spines on flexor margin. Pereopod 4 markedly shorter than pereopod 3; length of pereopod 4 merus about half that of pereopod 3.

Description. Carapace: Length (excluding rostrum) distinctly greater than breadth. Lateral margins slightly divergent, irregularly rugose behind base of cervical groove; without posterolateral ridge. Rostrum sharply triangular, exceeding one­third length of remaining carapace, margins unarmed; dorsum horizontal, apex faintly deflected dorsally. Anterolateral spine small; outer orbital angle produced to small acute spine extending to level of anterolateral spine. Dorsum smooth and unarmed, sparsely punctate, non­setose; occasionally with pair of low epigastric scales composed of transverse row of 3 or 4 minute granules. Pterygostomian flap with small anterior spine.

Sternum: Plastron broader than long, widening posteriorly. Sternite 3 (at base of maxilliped 3) strongly depressed, anterior margin narrow, deeply emarginate, with pair of median spines; outer lobes of emargination obtusely angled. Sternite 4 (at base of pereopod 1) with distinct anterolateral tooth extending anteriorly to level of base of emargination of sternite 3; surface granular; margins tuberculate, irregular.

Abdomen: Segments glabrous. Telson about two­thirds as long as broad; distal portion posteriorly emarginate, about twice length of proximal portion.

Eye: Cornea moderately dilated, subequal to length of peduncle; reaching to distal quarter of rostrum.

Antenna: Basal segment with distinct outer spine. Peduncle extending slightly beyond cornea. Flagellum about twice as long as peduncle. Ultimate and penultimate segments unarmed; ultimate segment about twice length of penultimate segment. Antennal scale slightly wider than opposite peduncular segments, slightly shorter to slightly longer than peduncle.

Maxilliped 3: Dactylus, propodus, carpus and merus unarmed. Crista dentata distinctly serrate on proximal two­thirds of ischium, extending onto basis.

Pereopod 1 (cheliped): Slender, cylindrical, about 3.5–4.0 times carapace length; chelae of adult females and juveniles usually slightly more slender than in adult males; segments glabrous dorsally and sparsely setose distally. Propodus with palm about 4 times as long as high, about 2.5 times as long as pollex. Fingers crossing, occlusal margins finely dentate; occlusal margin of dactylus with obtuse process proximally; occlusal margin of pollex with low prominence at about midlength. Carpus longer than merus and as long as propodal palm; glabrous. Inner and ventral margin of propodal palm, carpus and merus granular. Ischium with triangular spine on outer margin.

Pereopods 2–4: Sparsely setose. Meri dorsal margin proximally irregular. Propodi not broadened distally, with 6–10 movable spines on distal flexor margin, distalmost paired. Dactyli setose marginally, with 7–10 fixed, triangular spines on flexor margin, oriented oblique to dactylar margin.

Pereopods 2–3 similar, carpus about 0.5 merus length, about 0.6 propodus length. Pereopod 3 slightly longer than pereopod 2. Pereopod 4 markedly shorter than pereopod 3; length of pereopod 4 merus about half that of pereopod 3.

Ovum: 1.4–1.5 mm diameter.

Etymology. From the Greek, empheres, meaning ‘resembling’ or ‘like’ in reference to the strong resemblance of the present species with U. comptus Baba.

Remarks. Uroptychus empheres n. sp. closely resembles U. comptus Baba, 1988, from Borneo, but differs in subtle but consistent features: the carapace dorsum is glabrous, without any trace of tuberculation (except for the paired epigastric scales in some specimens); the posterolateral margin of the carapace does not bear a low ridge; the basal antennal segment bears a distinct outer spine instead of being only moderately produced as in U. comptus. Uroptychus empheres also resembles U. nigricapillis Alcock, 1901, described from the Andaman Sea, in most features including the spination of the dactyli of the walking legs, and form of the sternal plastron. Uroptychus nigricapillis differs from U. empheres, however, in having several small spines along the lateral margins of the carapace, epigastric spines on the carapace, singular instead of paired distal movable spines on the propodi of the walking legs and in having a shorter antennal scale that does not overreach the peduncle.

As in U. australis, the merus of pereopod 4 in U. empheres is about half the length of the merus of pereopod 3. Unfortunately, the relative lengths of the walking legs of U. comptus were not mentioned in the type description. The proportions of walking legs of the holotype, however, were kindly checked for us by Rafael Lemaitre (National Museum of Natural History, Smithsonian Institution) and found to agree with that of U. empheres and U. australis.

Sexual dimorphism in U. empheres is slight, being evident only in the slightly more robust chelae of males. Of the local species, U. empheres could be confused with U. australis and U. gracilimanus, but differs from both in bearing a field of granules on sternite 4. Part of the material reported by Poore et al. (1998) from the Tasmanian seamounts as U. australis is referable to U. empheres.

Distribution. Southern Ocean off southeastern Tasmania at 800 m depth.