Crocodiles

Crocodilians (crocodiles, alligators, gharials, caimans) are the last surviving archosaurs — the group that dominated the Mesozoic alongside dinosaurs. They have survived essentially unchanged for 200 million years through five mass extinctions. The Nile crocodile and saltwater crocodile are the world's largest living reptiles (reaching 7 meters, 1,000 kg) and are responsible for hundreds of human deaths annually. Crocodiles have one of the most powerful bite forces of any animal (3,700 psi), cannot chew (they swallow prey whole or drown it and wait for decomposition), and are surprisingly caring parents — females guard nests fiercely and carry hatchlings in their mouths to water. Their blood contains potent antibiotics active against antibiotic-resistant bacteria — research into crocodilian immune systems may yield new medicines.