The closest living relatives of crocodiles and alligators are, perhaps surprisingly, birds. They are both archosauriforms, a group of species that originated about 250 million years ago near the beginning of the Triassic period.
The group soon split into two lineages: one led to crocodiles (Pseudosuchia), while the other led to dinosaurs and then birds (Avemetatarsalia). This means there is a combined 500 million years of evolutionary change between modern birds and crocodiles, the Conversation reported.
