List of fossil bird genera

Birds evolved from certain feathered theropod dinosaurs, and there is no real dividing line between birds and dinosaurs, except of course that some of the former survived the Cretaceous–Paleogene extinction event while the latter did not. For the purposes of this article, a 'bird' is considered to be any member of the clade Aves sensu lato. Some dinosaur groups which may or may not be true birds are listed below under 'Proto-birds'.

This page contains a listing of prehistoric bird taxa only known from completely fossilized specimens. These extinctions took place before the Late Quaternary and thus took place in the absence of significant human interference. While the earliest hominids had been eating birds and especially their eggs, human population and technology was simply insufficient to seriously affect healthy bird populations until the Upper Paleolithic Revolution. Rather, reasons for the extinctions listed here are stochastic abiotic events such as bolide impacts, climate change due to orbital shifts, mass volcanic eruptions etc. Alternatively, species may have gone extinct due to evolutionary displacement by successor or competitor taxa – it is notable that an extremely large number of seabirds have gone extinct during the mid-Tertiary; this seems at least partly due to competition by the contemporary radiation of marine mammals.

The relationships of these taxa are often hard to determine, as many are known only from very fragmentary remains and due to the complete fossilization precluding analysis of information from DNA, RNA or protein sequencing. The taxa listed in this article should be classified with the "Fossil".

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