New specimens of Lithoptila abdounensis (Prophaethontidae) including long bones and fragments of mandibulae are described from the Upper Paleocene and Lower Eocene of the Ouled Abdoun Basin, Morocco. Elongated and slender wing bones suggest that this bird was an offshore or pelagic feeder capable of efficient flight. Lithoptila approximates Prophaethon in size but differs from the latter taxon in various features of the mandibula, coracoideum and femur. The anatomy and size of Lithoptila closely match those of Zhylgaia aestiflua, a putative shorebird (Charadriiformes) from the Upper Paleocene of Kazakhstan, known from two partial humeri. Consequently, we assign Zhylgaia aestiflua to the Prophaethontidae. The three species of Prophaethontidae inhabited tropical seas and most likely had comparable ecological niches.