Fishes of the family Caesionidae are restricted to the tropical Indo-Pacific region. They are planktivorous, thus differing widely in food habits from their nearest relatives, the lutjanine snappers, which are mostly benthic carnivores. This divergence is associated with morphological features that serve to characterize the Caesionidae: the upper jaw is highly protrusible, the ascending premaxillary process is a separate ossification, and the ethmo-maxillary ligament is absent.
Four caesionid genera and 6 subgenera are recognized and diagnosed. Four of these subgenera are newly described. Twenty species of caesionids are recognized and diagnosed, 5 of which are described as new.
The genus Caesio contains 8 species: C. striata and C. suevica, restricted to the Red Sea; C. varilineata n. sp., restricted to the Indian Ocean and Indonesia; C. xanthonota, restricted to the Indian Ocean, exclusive of the Red Sea, and Indonesia; C. cuning, found only from the eastern Indian Ocean to the western Pacific; C. lunaris, from the Indian Ocean to the western Pacific; C. caerulaurea, widely distributed from the western Indian Ocean to the south central Pacific; and C. teres, widely distributed from the Indian Ocean, exclusive of the Red Sea, to the south central Pacific.
The genus Pterocaesio contains 10 species: P. capricornis, restricted to the Indian Ocean, exclusive of the Red Sea; P. chrysozona, distributed widely from the Red Sea and coast of eastern Africa to the western Pacific; P. tile and P. marri, widely distributed from the Indian Ocean, exclusive of the Red Sea, to the south central Pacific; P. pisang and P. lativittata n. sp., distributed from the Indian Ocean, exclusive of the Red Sea, to the western Pacific; and P. digramma, P. randalli n. sp., P. tessellata n. sp., and P. trilineata n. sp. from the eastern Indian Ocean to the western Pacific.
The genera Gymnocaesio and Dipterygonotus are monotypic: G. gymnoptera is distributed from the Indian Ocean to the western Pacific; and D. balteatus is found from the western Indian Ocean, exclusive of the Red Sea, to the western Pacific.