Two new species of stargazers of the genus Uranoscopus (Teleostei: Uranoscopidae) from the western Pacific Ocean

Two new species of stargazers in the Uranoscopus albesca species-complex of the family Uranoscopidae are described from Papua New Guinea, which shares among other characters a concave posterodorsal margin of the pectoral fin. Uranoscopus brunneus n. sp. is described from a single specimen from off southwestern New Britain, and is characterised by lower edge of preopercle with 8 spines; labial fimbriae poorly-developed; anterior nostril with a long tubiform valve, posterior nostril a slit-like pore; supracleithrum with a sharp spine at rear end and five small spines inside; dorsoposterior margin of pectoral fin concave; 62 oblique scale-rows along the sides of the body in adult; pectoral-fin membranes dark brown. Uranoscopus kishimotoi n. sp., described from a single specimen from West Sepik Province, is characterised by the lower edge of preopercle with 3 spines; no labial fimbriae; both anterior and posterior nostrils with long tubiform valves; supracleithrum with a sharp spine at rear end and one additional small spine inside; dorso-posterior margin of pectoral fin concave; 59 oblique scale-rows along the sides of the body in adult; upper pectoral-fin membranes pale, lower membranes brown. The distribution of the species in the U. alb esca species-complex is discussed.


Introduction
The stargazers of the perciform fish family Uranoscopidae are a group of benthic living fishes distributed worldwide in tropical and temperate oceans, with a few species occasionally entering brackish water or even fresh water habitats. They bury in sand or mud, leaving only the eyes and anterodorsal part of the head exposed. Members of the group are characterised by having dorsally or dorsolaterally directed eyes placed on or near the top of a large, flattened, cuboid head; an oblique to vertical mouth, with lips usually lined with cutaneous cirri; and an elongate, subcompressed body (Pietsch 1989: 253). In the family, seven genera and 53 valid species are known Eschmeyer & Fong 2017).
The genus Uranoscopus is characterised by the presence of a small fourth infraorbital that covers only a relatively small portion of the sphenotic, only two extrascapular elements on each side of the posterior margin of the cranium, the posterior basibranchials unossified, an L-shaped toothplate associated with the ventral margin of the first epibranchial, and a venom gland associated with the cleithral spine (Pietsch 1989: 295). This genus is distributed in the Indo-West Pacific, in the eastern Atlantic and the Mediterranean and Black Sea. The genus comprises a total of 25 valid species  During the work on fishes of Papua New Guina which were collected during the PAPUA NIUGINI 2012 Biodiversity Expedition, the KAVIENG 2014 Expedition and the MADEEP Expedition, specimens of two undescribed species of Uranoscopus were discovered. These species are described in the present paper.

Methods and materials
The general methods follow Kishimoto (1984Kishimoto ( , 1987. The standard length is abbreviated as SL, the head length as HL. Values of paratypes in parentheses, following those of the holotype. The head length is measured from the tip of the upper lip to the end of the opercle; in addition, a length between the snout and the gill opening is measured. Counts of fin elements follow Fricke (1983). References are cited according to standards provided by Fricke & Eschmeyer (2017a). Institutional abbreviations follow Fricke & Eschmeyer (2017b).
Head moderate, anterior part of body moderately broad, depressed, body tapering and becoming compressed posteriorly. Body scales arranged in 62 oblique rows. Head, breast and belly naked. Anterodorsal area between lateral lines densely covered with scales just behind skull. Tubiform scales embedded along lateral line. Lateral line positioned dorsally, slightly bending down on caudal peduncle to continue in an extension on the sixth branched caudal-fin ray (counted from above), extending along the basal half of that ray. Spines 1-4 in first dorsal fin well developed, connected by membranes; rudimentary 5th element covered by skin. First two elements of second dorsal fin segmented and unbranched. Membranes of anal and paired fins fleshy and thickened. Pectoral fin broad, dorsoposterior margin concave, forming an angle of about 30° between upper edge and middle ray, remainder of distal margin nearly straight, 11th ray longest (Fig. 2 A). Soft dorsal and anal-fin bases long, height of soft dorsalfin 3.0 in second dorsal-fin base length, height of anal fin 3.4 in anal-fin base length. Caudal fin distally slightly convex. Pelvic fins situated on isthmus; distance between pelvic fin bases about one pelvic-fin base length. Pelvic spine feeble, closely connected to 1st soft-ray by connective tissue. Head flattened dorsolaterally, dorsal and lateral surfaces almost entirely encased in minutely sculptured bones. Externally apparent bones of head very slightly concave along mid-dorsal line. Preorbital spines 3, the uppermost spine forming a knob near anterior margin of orbit (Fig. 2 B). Single pair of basipterygial processes widely separated. Joints of head bone elements marked by narrow grooves. Post-interorbital knobs absent from frontal bone. Two parietal lobes developed. Preopercular limb not joined with opercle over most of its length, but contacts opercle posteriorly. Eye moderate, positioned dorsally, not telescopic, without membranous tentacle or grainy row. Interorbital fossa semi-oval, longer than broad, including anterior three-fifths of interorbital space, reaching to level of posterior end of pupil. Supracleithrum with a sharp spine at rear end and five small spines inside. Nasal bone weakly ossified, not exposed, covered by skin of snout. Frontal bones not forming a supraorbital tubercule. Anterior nostril with a wide, rounded flap, posterior nostril a slit-like pore (Fig. 2 B). No chin barbel or cirri on branchiostegal membrane. Prelingual filament reduced to a triangular velum. Opercle distinctly shorter than deep; subopercle without ventral thickening. Preopercle with a slight horizontal, oblique, ventro-lateral thickening. Lower edge of preopercle with 8 spines. Respiratory valve rudimentary. Dentary without a ventromedial flange. Teeth in jaws small, conical, in two series; one series of widely separated caniniform teeth on premaxillary and dentary; labial fimbriae poorly-developed, barely recognisable.
Colour in life (see Fig. 3). Dorsal parts of head and body dark brown, back scattered with irregular small rosy blotches. Sides of head and body dark brown, with irregular slightly larger rosy blotches. Belly and thorax rose, pectoral-fin base dark grey. Eye greenish. First dorsal fin black, base of first and second spines pale. Rays of second dorsal and anal fins grey, membranes spotted. Caudal-fin rays and membranes dark reddish brown. Pectoral fin black, distal margin reddish. Pelvic fin rose. Colour in preservative. Head brown; upper half of body dark brown, with numerous, closely set, pale blotches; ventral half of body yellowish, belly rose. Eyes dark grey. First dorsal fin jet black; second dorsal fin pale, rays spotted with brown. Anal fin yellowish. Caudal-fin rays yellow, spotted with brown, membranes pale. Pectoral-fin rays yellow, spotted with brown, membranes dark brown, tips of lower rays pale yellow. Pelvic fins dark grey, distal one-third of rays and membranes yellow.
Etymology. "Brunneus" (Latin) means brown; the name refers to the overall brown colouration of the species, and especially to its brown pectoral fin membranes.
Comparisons. This new species is a member of a species group which is characterised by a supracleithrum with a sharp spine at rear end and one or more spines inside, and the dorsoposterior margin of the pectoral fin distinctly concave (forming an angle of about 30-40° between upper edge and middle ray). The group is here named Uranoscopus albesca species-group; other species in this group are U. albesca, U. bauchotae, U. dollfusi and U. kishimotoi n. sp., which are compared in Tab. 2. Uranoscopus brunneus n. sp. exclusively possesses within the group a total of 12 anal-fin rays (other species 13-14), a very high number of 62 oblique scale rows along the sides of the body (other species 47-59), 8 spines on the lower margin of the preopercle (other species 3-6), and dark brown pectoral-fin membranes (other species: pale to light brown).
Remarks. This species was briefly described from the Philippines and Indonesia by Kishimoto (2001: 3529) as Uranoscopus sp. 2.
Uranoscopus brunneus n. sp. lives relatively deep, at a known depth range of 315−625 metres. Kishimoto (2001) reports a maximum total length of 26 cm, which would equal a maximum standard length of about 20 cm. The new species is close to U. kishimotoi n. sp. in having a high number of lateral scale rows and a very long cleithral spine.  Length between snout and gill opening in SL (% of SL Diagnosis. A small species of Uranoscopus with a moderately large head (head length 3.1 in SL); lower edge of preopercle with 3 spines; no labial fimbriae; both anterior and posterior nostrils with long tubiform valves; supracleithrum with a sharp spine at rear end and one additional small spine inside; dorso-posterior margin of pectoral fin concave; 59 oblique scale-rows along the sides of the body in adult; upper pectoral-fin membranes pale, lower membranes brown.
Head moderate, anterior part of body relatively narrow, slightly compressed, body tapering and becoming strongly compressed posteriorly. Body scales arranged in 59 oblique rows. Head, breast and belly naked. Nape with embedded scales which are barely visible. Tubiform scales embedded along lateral line. Lateral line positioned dorsally, slightly bending down on caudal peduncle to continue in an extension on the fifth branched caudal-fin ray (counted from above), extending along the basal one third of that ray. Spines 1-4 in first dorsal fin well developed, connected by membranes; rudimentary 5th element covered by skin. First element of second dorsal fin segmented and unbranched. Membranes of anal and paired fins fleshy and thickened. Pectoral fin broad, dorsoposterior margin concave, forming an angle of about 40° between upper edge and middle ray, remainder of distal margin straight, 10th ray longest (Fig. 2 C). Soft dorsal and anal-fin bases moderately long, height of soft dorsal-fin 1.9 in second dorsal-fin base length, height of anal fin 3.4 in anal-fin base length. Caudal fin distally convex. Pelvic fins situated on isthmus; distance between pelvic fin bases about half a pelvic-fin base length. Pelvic spine feeble, closely connected to 1st soft-ray by connective tissue. Head flattened dorsolaterally, dorsal and lateral surfaces almost entirely encased in minutely sculptured bones. Externally apparent bones of head not concave but flattened along mid-dorsal line. Preorbital spines 3, the upper two spines forming small knobs near anterior margin of orbit (Fig. 2 D). Single pair of basipterygial processes widely separated. Joints of head bone elements not marked by grooves. Post-interorbital knobs absent from frontal bone. Parietal bone not separated into lobes. Eye small, positioned dorsally, slightly telescopic, without membranous tentacle or grainy row. Interorbital fossa semi-oval, longer than broad including most of interorbital space, nearly reaching to level of posterior end of orbit (Fig. 5 B). Supracleithrum with a sharp spine at rear end and one additional small spine inside. Nasal bone weakly ossified, not exposed, covered by skin of snout. Frontal bones not forming a supraorbital tubercule. Both anterior and posterior nostrils with long tubiform valves (Fig. 2  D). No chin barbel or cirri on branchiostegal membrane. Prelingual filament reduced to a barely distinguishable triangular velum. Opercle distinctly shorter than deep; subopercle without ventral thickening, not overlapping opercle. Preopercle without a ventro-lateral thickening. Lower edge of preopercle with 3 large spines. Respiratory valves well developed. Dentary without a ventromedial flange. Teeth in jaws small, conical, in two series; one series of widely separated caniniform teeth on dentary, no caniniform but small villiform teeth on premaxillary; no labial fimbriae.  Colour in life (see Fig. 6). Dorsal parts of head brown, and of body dark brown, with irregular large yellowish blotches, turning to oblique yellowish to rose streaks on the sides of the body. Belly, thorax and pectoral-fin base rose. Eye dark brown. First dorsal-fin black. Second dorsal, anal and caudal fin rose. Pectoral fins red. Pelvic fins rose.
Colour in preservative. Head yellowish; upper half of body brown, with numerous, closely set, pale blotches; ventral half of body yellowish, belly whitish. Eyes dark grey. First dorsal fin jet black; second dorsal fin pale, rays light grey. Anal fin yellowish, membranes whitish. Caudal-fin rays yellow, distally grey, membranes translucent. Pectoral-fin rays yellow, spotted with brown, upper membranes pale, lower membranes brown, tips of lower rays and membranes pale yellow. Pelvic fins yellow.   Etymology. The new species is named in honour of Hirokazu Kishimoto, appreciating his important research on uranoscopids; he already recognised the existence of the two new species which are described in the present paper.
Comparisons. This new species is a member of the Uranoscopus albesca species-group (comparison of the species of this group see Tab. 2). Uranoscopus kishimotoi n. sp. exclusively possesses within the group a compressed head (other species depressed or as broad as deep), 3 spines on the lower margin of the preopercle (other species 4-8), a single small additional spine on the inner side of the supracleithrun (other species 2-5), and a long, tubiform valve on the posterior nostril (other species with a slit-like pore, without a valve).
Uranoscopus kishimotoi n. sp. lives relatively deep, at a known depth range of 300-308 metres. Kishimoto (2001) reports a maximum total length of 18 cm, which would equal a maximum standard length of about 14 cm. The new species is close to U. brunneus n. sp. in having a high number of lateral scale rows and a very long cleithral spine.

Discussion
The species of the Uranoscopus albesca species-complex, which share (among other characters) a concave dorsoposterior margin of the pectoral fins, have disjunct distributions in the eastern Atlantic and the Indo-West Pacific (Fig. 7). A single species (U. albesca) is found in the eastern Atlantic from Senegal to Angola; two species occur in the northern Red Sea (U. bauchotae and U. dollfusi), and the remaining two are widespread in the East Asian Archipelago (U. brunneus n. sp. and U. kishimotoi n. sp.). The absence in most parts of the Indian Ocean is apparently due to a relict distribution pattern of the U. albesca complex, as the highest number of species in the genus Uranoscopus is found in the Indian Ocean (Fricke et al. 2013), and this is probably where most of the evolution of specialised species has been recently going on. Such newly evolved species may have driven species in the U. albesca complex towards the margins of the general distribution range of the genus.