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. The coral snake is highly poisonous and resembles a number of nonpoisonous snakes. It does not have fangs and has round pupils.