Developmental series of two sympatric flounders of the genus Paralichthys, found in the Bay of Coquimbo, are illustrated and described. The series consist of yolksac to metamorphosed larvae of artificially-reared Paralichthys adspersus (1.7-13.0 mm SL) and P. microps (1.5-11.0 mm SL). Field-collected larvae correspond to the size ranges found in reared larvae. Degree of cephalic spination (in particular, sphenotic spines), pigmentation pattern, and number of elongated dorsalfin rays are useful for identification of yolksac-to-postflexion larvae of both species. During early metamorphosis the most valuable characteristics for identification are the number of elongated dorsal-fin rays, although after their reabsorption several morphometric relationships have to be used. Paralichthys adspersus preflexion larvae have two sphenotic spines and almost no pigmentation in the dorsal finfold, while P. microps larvae have only one sphenotic spine and a well-pigmented dorsal finfold. Beginning at notochordal flexion, the number of elongated dorsal-fin rays, six for P. microps and three for P. adspersus, can be used to identify the larvae. During late metamorphosis, morphometric relationships of SnL/HL, HL/SL, and BD/SL must be used to identify the larvae. Flexion is complete at 7.2 mm SL and metamorphosis at approximately 11.0 mm SL in P. microps, and at 8.6 mm SL and 13.0 mm SL in P. adspersus, respectively.
