Bird footprint fossils, or ichnofossils, can be found in strata dating back 166 million years, beginning in the Jurassic period of the Mesozoic era. True birds of the class Aves evolved during the Cretaceous period, with fossils known from 72 million years ago and DNA evidence suggesting an origin earlier in the period. Footprint fossils can rarely be identified to the species that created them.
