Members of this family are the best-known venomous snakes. Viperids typically have broad, triangular heads. Most are also heavy-bodied with relatively short, stender tails.
Most vipers have numerous and heavily keeled body scales.
Their long fangs permit deep penetration and envenomation of prey. The hinged-fang mechanism allows their storage against the roof of the mouth when not in use. The pit-organs of the crotalines lie on each side of the head between the nostril and eye and contain infrared receptors. They allow the snake to detect prey whose body temperature differs from background temperatures Echis carinatus. As indicated by their wide distribution, vipers can be found in most ecological habitats from tropical rain forests to deserts and even high mountains.