Abstract
A new species of scorpionfish, Poseidon's scorpionfish Parascorpaena poseidon, is described on the basis of ten specimens collected from southwestern Taiwanese waters ranging from Penghu to Chufongbi, Pingtung. The morphological and molecular analyses reveal the new species is clearly separated from the two similar species, P. aurita and P. mossambica. Parascorpaena poseidon is distinguished from congeners by the following combination of characters: three equal-sized suborbital spines without ridge; supraocular tentacle absent or very short; pectoral-fin rays 15-16 (usually 16); pored lateral-line scales 22-26 (usually 22-23); longitudinal scale rows 43-47; pre-dorsal-fin scale rows 2-3 (usually 3); 10-12 scale rows between 6th dorsal-fin spine base and lateral line; 10-12 scale rows between the last dorsal-fin spine base and lateral line; total gill rakers 15-16, gill rakers on hypobranchial 2-3; ratio of 11th and 12th dorsal-fin spine 60%-81% (mean 73%); blackish spots randomly distributed on all fins; absence of a distinct black blotch on spinous dorsal fin in male; body size relatively large.