Genus Pteroidichthys Bleeker, 1856

Pteroidichthys Bleeker, 1856: 33 (type species: Pteroidichthys amboinensis Bleeker, 1856; type by original description, monotypic; gender: masculine).

Pteropelor Fowler, 1938: 77 (type species: Pteropelor noronhai Fowler, 1938; type by original description; monotypic; gender: neuter).

Diagnosis. A genus of the family Scorpaenidae with the following combination of characters: body strongly compressed, body width 10–24% of SL, and elongated, body depth 28–40% of SL; 12 dorsal-fin spines; no palatine teeth; tympanic spines present; upper posttemporal spines absent; body scales cycloid; lower pectoral-fin rays not strongly notched, not filamentous; no black blotches on lower caudal fin.

Remarks. The scorpionfish genera, Pteroidichthys, Hipposcorpaena Fowler 1938, and Rhinopias Gill, 1905, are closely related to each other (Motomura & Senou, 2005; Motomura & Johnson, 2006); Pogonoscorpius Regan, 1908 is a junior synonym of Rhinopias (Motomura unpub. data). These genera are distinguished from all other genera of the family Scorpaenidae by having 12 dorsal-fin spines, a strongly compressed body, cycloid body scales, and no teeth on the palatines (Poss, 1999; this study). Pteroidichthys differs from Hipposcorpaena and Rhinopias in having a shallower body depth [28–40% of SL vs. 40–53% of SL in the latter two genera, data from Motomura & Senou (2005) and Motomura & Johnson (2006); 38–54% of SL from Poss (1999)], tympanic spines present (vs. spines absent in Rhinopias), and the lower pectoral-fin rays not strongly notched (vs. strongly notched, forming filaments in Hipposcorpaena), and in lacking upper posttemporal spines (spines present in Rhinopias) and lacking black blotches on the lower caudal fin (1–4 distinct blotches present in Hipposcorpaena) (Motomura & Senou, 2005; Motomura & Johnson, 2006).

The genus Pteropelor was originally described by Fowler (1938) for his new species, Pteropelor noronhai, from off Hong Kong, China. Although Chen & Liu (1984) and Mandrytsa (2001, 2002) treated it as a valid species of Pteropelor, Poss (1999) and Motomura et al. (2011a) regarded it as a species of Pteroidichthys . Fowler (1938) stated that Pteropelor is similar to Pteroidichthys but differs in “its incised spinous dorsal membranes, absence of barbels, and large scales”. However, these general characters usually represent species-level differences in the family Scorpaenidae . In addition, differences in the number of anal-fin spines (2 vs. 3) and the condition of the dorsal-fin spines (flexible vs. rigid) found between P. amboinensis and P. noronhai might be thought equal to generic features, but characters of a newly described species in this study, P. caussei, represent an intermediate condition between the two species, i.e., having 3 anal-fin spines and rigid dorsal-fin spines. Thus, Pteropelor is herein regarded as a junior synonym of Pteroidichthys, and P. noronhai is treated as a valid species of Pteroidichthys .