The Viperidae family, commonly known as vipers, constitute a large family of venomous snakes, which are found in all continents. The vipers belong to the order Squamata (scaled reptiles). They are also grouped in the suborder Serpentes. All vipers have one common physiological trait; they all secrete cytotoxic/hemotoxic venom, which is different from the neurotoxic venom produced by the secretory glands of the Elapidae family.
The Viperidae family includes 11 major genera: Agkistrodons (moccasins), Azemiops, Bitis, Bothrops (lanceheads), Crotalus (rattlesnakes), Gloydius, Lachesis (muta), Ovophis, Porthidium (hognoses), Trimeresurus, and the Viperinae (viperines). However, some serpentologists group all the azemiops and viperines as two separate subfamilies. Nevertheless, the majority of them assort these snakes into two genera of the Viperidae family.
The vipers of the genus Agkistrodons are found only in North America. The Bothrops and Lachesis snakes are common in Central and South America, while the different species of genus Crotalus, the rattlesnakes, are found throughout the whole American continent, from Canada to Argentina. The Bitis inhabit Africa, and the snakes from the genera Azemiops, Gloydius, and Ovophis are found only in Asia, from the Ural region of Russia, to Vietnam and Japan.
Common Characteristics
All the vipers are venomous snakes, injecting cytotoxic/hemotoxic venom, which breaks down body tissues, causing areas of necrosis and sometimes clots in the bloodstream. When their venom gets into the bloodstream, it becomes systemic and affects the organs, causing kidney failure, for example. This is due to the proteases it contains. In other words, the venom is a powerful enzyme that aids the vipers to digest the prey they catch.
They have a pair of long, curved, hollow fangs, which are not retractable, as is the case with the Elapids's fangs. Their venom sacs (glands) lie at the rear of the upper jaw, right behind their eyes. Their maxillary (upper jaw) is unhinged from the lower jaw, making it possible for the snake to swallow large prey. Most of snakes of this family have vertical, slit-shaped eye pupil.
Below, a a diamond-back rattlesnake, very common in North America, a member of the genus Crotalus.
