Nonpoisonous snakes usually leave a series of small, shallow puncture wounds because they have teeth instead of fangs. The exception is the coral snake, which leaves a semicircular marking from its teeth. Because some poisonous snakes also have teeth, fang and teeth marks may be apparent. The presence of teeth marks does not rule out a poisonous bite, but the presence of fang marks always confirms a poisonous snakebite. The two fangs of a poisonous snake are hollow and work like a hypodermic needle.
Pupils resemble vertical slits.
Presence of a pit. Pit vipers have a telltale pit between the eye and the mouth. A triangular or arrowhead shaped head. The rattlesnake often shakes its rattles as a warning. One snake that is not a pit viper snake but is poisonous is the coral snake.