Ratabulus megacephalus

description

Description. Dorsal fin rays I + VIII + I- 11 or 12 or I + IX + 0 - 11 (I + IX + 0 - 11 in one, I + VIII + I- 12 in one); anal fin rays 12; pectoral fin rays two or three (usually two) + 9 – 11 + 6 – 8 = 19 or 20; pelvic fin rays I, 5; branched caudal fin rays 12 or 13; scales in lateral line 53 – 55, anterior three or four scales with spine; posteroventrally slanted oblique scale rows above lateral line 71 – 78; anteroventrally slanted oblique scale rows above lateral line 94 – 112; gill rakers 1 + 6 – 8 = 7 – 9. See table 1 for selected proportional measurements. Head length 2.4 – 2.7 in SL. Snout rather long, its length 2.8 – 3.2 in HL, ratio as % HL markedly decreasing proportionally with growth (fig. 9). Iris lappet broad and simple dorsally and absent ventrally (fig. 5 b). Interorbital width 12.8 – 19.6 in HL. Nasal bone with 0 – 2 spines, and without tubercles (fig. 4 b). Lachrymal with 2 – 4 spines directed anterolaterally. Preocular spine in front of eye, its base without spines or tubercles. Suborbital ridge with many small to large spines; anteriormost (preorbital) spine usually present. Supraorbital ridge serrated medially and posteriorly or just posteriorly. Postocular

Taxonomic revision of the genus Ratabulus (Teleostei: Platycephalidae), with descriptions of two new species from Australia

diagnosis

Diagnosis. A species of Ratabulus with 94 – 112 anteroventrally slanted oblique scale rows above lateral line; snout length 31.2 – 35.7 % HL, markedly decreasing in length proportionally with growth; pectoral fin length 13.9 – 17.0 % SL; pelvic fin length 19.5 – 23.1 % SL; nasal bone without tubercles; dorsal surface of head and body dark brown, with small, round, dark-brown spots; and pelvic fin with small brown to black spots.

Taxonomic revision of the genus Ratabulus (Teleostei: Platycephalidae), with descriptions of two new species from Australia

discussion

Remarks. R. megacephalus is most similar to R. fulviguttatus in having the nasal bone devoid of tubercles (versus tubercles present in R. diversidens and R. ventralis) (fig. 4) and the dorsal surface of the body with small, round spots (versus without spots) (fig. 2). R. megacephalus differs from R. fulviguttatus in having a proportionally longer snout (31.2 – 35.7 % HL in R. megacephalus versus 30.4 – 34.8 % HL in R. fulviguttatus) and shorter pectoral fins (13.9 – 17.0 % SL compared to 14.6 – 16.5 % SL) (figs 9 – 10) at comparable sizes, and the dorsal surface of the head and body dark brown (versus pale brown) (fig. 2). R. megacephalus is also separable from R. ventralis in having shorter pectoral fins (13.9 – 17.0 % SL versus 15.8 – 18.6 % SL) and pelvic fins (19.5 – 23.1 % SL versus 25.3 – 28.2 % SL) (figs 10 – 11). Sadovy and Cornish (2000) reported Ratabulus megacephalus from Hong Kong, but their photograph depicts a specimen of Inegocia ochiaii Imamura, 2010, previously known incorrectly as ‘ Inegocia guttata ’ (e. g. Matsubara and Ochiai, 1955; Ochiai, 1984), a species that has an interopercular flap, and a long and branched iris lappet.

Taxonomic revision of the genus Ratabulus (Teleostei: Platycephalidae), with descriptions of two new species from Australia

distribution

Distribution. East and South China seas, and Northwest Pacific, including southern Japan, Korea, Taiwan, Hainan Island and northern Philippines, at depths of 192 – 218 m (Anonymous, 1962; Ochiai, 1984; Shao and Chen, 1987, 1993; Knapp, 1999; Kim et al., 2005) (fig. 1).

Taxonomic revision of the genus Ratabulus (Teleostei: Platycephalidae), with descriptions of two new species from Australia