Several lineages of modern birds existed, though many were of lineages that differed profoundly from their relatives of today and thus are not their ancestors, but became extinct in the Cenozoic.
Existían varias liñaxes de aves modernas, aínda que moitas eran liñaxes que diferían profundamente dos seus parentes de hoxe en día e non son os seus antepasados, pero extinguíronse no Cenozoico.