TAXONOMY
Many families of snakes include primitive blind, burrowing species not commonly seen as pets. Others include only one species. This book will refer to only four major families: Boidae, Colubridae, Elapidae, and Viperidae.
The Boidae and Colubridae contain the species most commonly seen in veterinary practice.Table 5.1 Examples of common snake families
| Family | Common name | Approx. no. of species | Species examples |
| Viperidae | Viper | 227 | Rattlesnake, Pit viper, Puff adder |
| Elapidae | 290 | Mamba, Cobra, Tigersnake, Brownsnake, Taipan, Sea snake | |
| Colubridae | Typical snakes | 1700 | Boomslang, Cornsnake, Rat snake, Kingsnake, Milksnake, Garter snake |
| Boidae | 63 | Boa constrictor, Anaconda, Royal python |
Boidae
These include the giant snakes, such as the anaconda and reticulated python. There are two main groups - the boas, which are viviparous and come from North, South, and Central America, and the oviparous pythons from Africa, Asia, and Australia.
These are powerful constricting snakes, which are often popular pets due to their docility. They are the most primitive of snakes, having vestigial spurs, two carotid arteries, and a coronoid bone (this part of the jawbone is absent in the more advanced species). They also have two lungs, some possess a cecum, and have shorter tails. Many have specialized infrared pit receptors on the upper and lower labial scales (Bellairs 1969d; Pough 1998a).
Colubridae
This family are the so-called typical snakes and comprises 70% of snake species (1700 species) (Pough 1998a). These are the most widely distributed (although they are not found in Australia) and are especially common in North America. They range from arboreal to aquatic to terrestrial. Some species, like the Boomslang (Dispholidus typus), are rear fanged but most species are harmless. These more advanced snakes have evolved to having only one functional right lung and a single left carotid artery.
Elapidae
These snakes are closely related to the colubrids but are probably more advanced. They have small heads and front fangs and include some particularly venomous species, such as the cobras and mambas. The group includes a lot of Australian species which have filled niches not occupied by vipers and colubrids. They are mostly oviparous. Like the colubrids, they have only one functional right lung and a single left carotid artery (Pough 1998a).
Viperidae
The vipers are the most advanced snakes in evolutionary terms and are found everywhere except Australia because they evolved after that landmass broke away. They tend to be short and stocky, with broad heads and may be oviparous or viviparous. The have only one carotid artery, one right lung, and a short hinged maxilla that allows the front fangs to be erected. The subfamily Crotalinae, which includes pit vipers and rattlesnakes, have heat-sensitive receptors between the eyes and nostrils. The rattlesnake has a rattle composed of keratin left over after shedding (Pough 1998a).