Blueskin

description

Description. Counts and proportional measurements as percent of SL of the holotype and other specimens (included as synonymized type) of Polysteganus lineopunctatus are given in Table 1. Body depth relatively deeper; head robust, rostro-occipital profile strongly convex; interorbital scaly, scales extending to nearly above anterior nostrils and just above posterior nostrils, anterior nostrils small and rounded, posterior nostrils oval; orbit diameter greater than interorbital width; maxilla naked, its posterior end not reaching vertical at front edge of eye, rear margin of maxilla not concealed by infraorbitals; jaws robust, especially upper jaw; canines slender and very short, 4 in upper and 6 in lower jaw (two outermost canines in upper jaw larger than 2 medial canines, and two outermost canines of lower jaw larger than 4 medial canines; an outer lateral row of conical teeth and a series of villiform teeth on inner side of outer lateral teeth row; mandibular profile slightly convex; rear margin of preopercle rounded and feebly serrated, a narrow naked area (preopercle with keel-like ridge), between preopercle flange scaly area and cheek scales; first to third dorsal-fin spines pr

Redescriptions of Polysteganus coeruleopunctatus (Klunzinger 1870) and P. lineopunctatus (Boulenger 1903), with two new species from Western Indian Ocean

diagnosis

Diagnosis. Distinguished from all congeners of Polysteganus by the following combination of characters: scale rows above lateral line 7 ½; scales rows between 5 th dorsal-fin spine base and lateral-line 5 ½; higher counts of pored lateral-line scales (53 – 55); suborbital depth clearly less than or subequal to orbit diameter; dorsal-fin rays reddish pink or orangish red but with deep yellow upper margin of dorsal-fin rays; 7 or 8 distinct irregular lines of blue spots on body (often present even in preserved specimens); pale reddish yellow membranes on caudal-fin lobes and caudal fin with hyaline white margin on lower fin lobe; no blue iridescence on dorsal and lateral side of whitish pink body; canines somewhat smaller, only upper canines visible when mouth closed; body slender, 40 – 43 % (mean 42 %) of SL; no bony bulge before and above eye even in larger specimens of over 25 cm TL; caudal fin moderately forked.

Redescriptions of Polysteganus coeruleopunctatus (Klunzinger 1870) and P. lineopunctatus (Boulenger 1903), with two new species from Western Indian Ocean

discussion

Remarks. Polysteganus lineopunctatus has long been considered a junior synonym of P. coeruleopunctatus (Klunzinger 1873) but is justified as a valid species in this study. The counts and proportional measurements of type material show it to be different (Table 1). Genetic data (Fig. 4) also supports the validity of P. lineopunctatus. Polysteganus lineopunctatus differs from P. coeruleopunctatus in having 5 ½ scales rows between 5 th dorsalfin spine base and lateral line (vs. 5 ½ or 6 ½ scale rows in the latter); 53 – 55 pored lateral-line scales (vs. 50 or 51 pored lateral-line scales); very weak bony bulge before and above eye, forming a low median ridge (vs. weak bony bulge, becoming prominent in specimens over 25 cm SL); anal-fin rays whitish pink (vs. anal-fin rays pinkish basally); with 7 or 8 distinct irregular blue spotted lines on small to large adults (vs. 7 or 8 faint irregular blue spotted lines).

Redescriptions of Polysteganus coeruleopunctatus (Klunzinger 1870) and P. lineopunctatus (Boulenger 1903), with two new species from Western Indian Ocean

distribution

Distribution. Polysteganus lineopunctatus (Boulenger 1903) is currently known only from South Africa and Mozambique, and is endemic to the southwestern Indian Ocean. No confirmed reports of this species from Madagascar.

Redescriptions of Polysteganus coeruleopunctatus (Klunzinger 1870) and P. lineopunctatus (Boulenger 1903), with two new species from Western Indian Ocean