Vipers are highly poisonous snakes. Their huge venomous glands make their heads appear a wide triangle. Vipers can control the movement of their fangs. Sometimes only one of them is used to inject venom. Vipers are the most progressive snakes. Buccal pit free vipers have huge and hollow teeth, which are full of venom.
The viper's teeth are attached to the flexible upper jaw and can be folded and retracted when not in use. The rattlesnake is a viper with buccal fossa, which is located between each nostril and eye. It can be used to sense infrared rays and detect warm blooded animals. This kind of snake is named after its tail, which can make sound. It is mainly distributed in North America.