One major difference between a lion and a crocodile is that the lion is a mammal, and the crocodile is a reptile. A lioness gives birth to live young and nurses them with her milk. A crocodile lays eggs and covers them with rotted vegetation to keep them warm. After the baby crocodiles are born, she looks after them until they can fend for themselves.
As a mammal, the lion is warm blooded and has fur. Since the crocodile is cold blooded, its body temperature is dependent on the environment. A crocodile warms its body by basking and cools its body by finding shade or entering the water. A crocodile is also covered with bony plates called scutes instead of fur.
A crocodile, though air breathing, is adapted to spending much time in the water, while the lion is terrestrial. The crocodile can grow to be larger than the lion. The Australian saltwater crocodile can be 23 feet long and weigh over a ton. The male lion can be between 8 and 11 feet long and weigh over 400 pounds.
Crocodiles live much longer than lions. A crocodile can live to be 100 years old. A male lion may live for only 10 years, while a female may live for up to 16 years.