Crocodile is one of the earliest and most primitive reptiles found alive by human beings so far, also known as the living fossil of the biological world, with an average life span of about 150 years. Crocodiles are tall reptiles. They breathe with their lungs, which is similar to mammals. It is also a good indication that mammals evolved from reptiles. Shown here is the Siamese crocodile (Crocodylus siamensis), a medium-sized crocodile that can reach up to four meters in length as an adult. Their temperament is relatively docile, easy to be tamed. With the help of humans, they can also perform thrilling performances with people. We often say “crocodile’s tears”. Because crocodiles don’t have sweat glands, they can only shed excess salt through tears or lubricate their eyes.