The highly venomous Gaboon Viper (Bitis gabonicus) , from western Africa, is possibly the heaviest viper (family Viperidae) in the world (at up to 174 cm/69 in and 20 kg/44 lbs), and has the longest fangs of any venomous snake (at 2 - 2.5 inches in length).
(photos: T - Esther Simpson; B - Tim Vickers)