Abstract New material from the Santa Marta Formation (late Coniacian-?early Maastrichtian) of James Ross Island contributes significantly to the current knowledge of Late Cretaceous Antarctic fish diversity. The taxon list for the Santa Marta Formation is extended, and new records of neoselachians and teleosts are reported. The stratigraphic ranges of some previously known taxa are enlarged, and the palaeobiogeography and palaeoecology of Late Cretaceous Antarctic fishes are discussed. Top predators that occupied the higher levels in the food chain along with marine tetrapods dominate the marine faunas from the Santa Marta and López de Bertodano formations. The only fish adapted to crushing hard-shelled invertebrates were the chimeroids. Rays, an important component of marine fish associations, as well as fish from lower trophic levels, remain unknown from the Late Cretaceous of Antarctica.