The Mexican horned pitviper (Ophryacus undulatus) is a rare, venomous snake about which very little is known. It can be easily distinguished from most other vipers by the raised scales above its eyes, giving the appearance of horns (3).
The Mexican horned pitviper varies in colour throughout its range, from grey to green on the upperparts (3), typically with yellowish underparts (2). There is an irregular, darker zigzag pattern along its back (2) (3).
Like other vipers (species in the Viperidae family), the Mexican horned pitviper has a triangular-shaped head, vertical pupils, and long, pointed, curved fangs. The fangs are hinged, allowing them to lie flat against the roof of the mouth when the mouth is closed, and then rotate forward when the viper is ready to strike. Venom, produced in glands at the back of the head, flows through the fangs into the prey (4).
Pitvipers are named after the pair of small pits situated between the eye and nostril. These pits are sensitive to heat, helping the Mexican horned pitviper to locate warm-blooded prey (4).
- Snout-vent length: 23 - 60 cm (2)
- Tail length: 4 - 7.7 cm (2)
- Head length: 1 - 1.6 cm (2)