Shark's sharp teeth, whose initial function was only to catch and bite food, evolved into mammals, and teeth gradually had many functions such as cutting, piercing, tearing and grinding. The evolution process of animal teeth is from the same teeth with the same size and shape in mammals to irregular teeth with different sizes and functions. After shedding, the redundant teeth regenerate, and the regenerated teeth are only changed once in a mammal's life. From the end or side tooth of a mammal to the slot tooth; It is widely distributed in the upper and lower jaws.
Animals' teeth are diverse and have their own characteristics. Like other sharks, ferret sharks have rows of teeth. When teeth wear out, new teeth will be born immediately to replace the old ones. In a year, ferrets and sharks can wear or lose 1500 teeth. The sharp teeth of the ferret shark can help it bite open the turtle shell and bite off a large piece of meat from fish, seals and even whales; The snake's teeth are too big to put in its mouth. This kind of tooth can pierce the shell of crustaceans. A poisonous snake can open its mouth twice the normal size. By studying the teeth of animals, we can know their feeding habits and age, and it is also an important index to study the body function and structure of animals.