what era/period birds
Paleontology portal. Cretaceous period birds â in the Mesozoic Era. The Cretaceous is a geologic period and system from circa 145 Â± 4 to 66 million years (Ma) ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the Cenozoic era.