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Viperidae: 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 structure of the hinge mechanism is unique; the lateral process of the palatine bone is absent, each maxilla is cuboidal and bears a single enlarged maxillary tooth (several replacement fangs lie behind the functional fang), the maxillary fang has a duct on its anterior face, and the elongate ectopterygoid serves as a lever to erect or depress the fang. 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. |
