No, crocodiles are oviparous animals. Some crocodiles decide their sex because of temperature. Mammals, on the other hand, have hair and heart, and breathe by lungs to keep a constant temperature. Dolphins, moles, bats and so on. There is also a kind called "viviparous", as the name implies, that is, there are eggs first, and then viviparous. Some poisonous snakes and sharks are viviparous, lay eggs in the mother's womb, hatch their offspring, and then give birth.