In the current study we provide information to aid in the identification of bivalve larvae in plankton samples based on the descriptions of recently settled spat of Zygochlamys palagonica and Hiatella meridionalis, 2 conspicuous bivalves commonly distributed in the shelf-break frontal system of the Argentine Sea. The first species is of particular interest given that it has been commercially exploited since 1996, and the phase between gamete release and larval settlement was unknown. We provide empirical evidence of a planktotrophic development for the larvae of both species.