Warm blooded (endothermic) dinosaurs are currently thought to have been the majority, or possibly even the entirety. Crocodilians (alligators, crocodiles, etc)

Warm blooded (endothermic) dinosaurs are currently thought to have been the majority, or possibly even the entirety. Crocodilians (alligators, crocodiles, etc) likely diverged from endothermic dinosaurs, as they have features shared with other endothermic animals and not with ectotherms (cold-blooded animals) such as 4-chambered hearts.