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They are known from fossil and subfossil remains only, and in a few cases may be remembered in folk memory. Such birds are here presented in 2 articles, separated according to the rough date of extinction and the possibility of human influence in their extinction:
- Fossil birds deals with birds from pre-human prehistory, from the earliest Proto-birds to the ancestors of modern species. Famous examples are Archaeopteryx, Argentavis, Confuciusornis, Hesperornis, the "terror birds", Osteodontornis, and Pelagornis sandersi.
- Late Quaternary prehistoric birds are birds which have gone extinct in the last 30-10,000 years or so, and in most cases human activity is at least complicit in their disappearance. Some are known from native tales, others are tentatively suggested to have lasted into the age of written history. These include, for example, a species of mihirung, the moa and Haast's eagle, and Merriam's teratorn.
New evidence that birds are the living descendants of the Theropoda dinosaurs changed the view we thought that how dinosaur may have looked like. The first bird archeopteryx had many similarities with birds as well as Theropoda dinosaurs. This bird was a link between Theropoda dinosaurs and birds. But,fossil records show that Theropoda dinosaur groups like Dromaeosauridae, Compsognathidae, Oviraptorosauria, Therizinosauridae and even Tyrannosauroidea which were likely to had feathers made the evidence that these were theropds and even prehistoric basal birds.