Snake

FAMILY LEPTOTYPHLOPIDAE (slender blind snakes)

This family of snakes is composed of 50 species in two families. They are generally regarded as the most primitive snakes, having a pelvic girdle and vestiglial hind limbs. They have a single lung and oviduct and are well adapted to their burrowing life style. They feed exclusively on small invertebrates such as ant and termite larvae. Leptotyphlopids are oviparous.

There are two species of this family in North America.

FAMILY BOIDAE (boas and pythons)

Boidae is a large family of snakes that includes all five of the world's giant snakes. Boids are an ancient family that are characterized by a mixture of modern and primitive traits. They have flexible jaws found in more advanced families but also retain a pelvic girdle, vestigial hind limbs, and many use both lungs. While there are close to one hundred species of boids worldwide, there are only two species of boas found in North America, both in the sub-family Eryciniae.

COLUBRIDAE (colubrid snakes)

The Colubrid snakes are sometimes refered to as "typical snakes". They comprise the largest family by far with over 2000 species worldwide. Most are medium sized snakes, and all lack a pelvic girdle and have no vestigial hind limbs and whose left lung is either absent or greatly reduced. Most species are considered members of two large subfamilies, Colubrinae and Natricinae which are distinguished by the presence (Natricinae) or absence (Colubrinae) of spines on the lumbar vertebrae. Both subfamilies contain over 200 genera. The Colubrinae subfamily includes two of the genera popular with herpetoculturists, Elaphe and Lampropeltis. The Natricinae subfamily includes water snakes (Nerodia) and garter snakes (Thamnophis) among others. With a family this large, there will always be disagreements about classification, especially regarding the numbers and types of subspecies.

ELAPIDAE (cobras and coral snakes)

The cobra family is thought to have evolved from Colubrid snakes and many appear very similar in appearance with long, slender bodies and large scales (plates) on the head. They differ in having more advanced venom delivery systems than the venomous Colubrids. Elapids have fangs that are "effectively tubular" in that the fangs contain grooves that are enclosed by an infolding of the edges. The fangs are in the front of the mouth rather than the rear as is seen in venomous Colubrids. The Elapidae contains some of the world's most dangerous snakes including cobras (Naja), mambas (Dendroaspis) and sea snakes (Hydophinae and Laticaudinae). Elapids are found worldwide and in Ausralia are the predominant family. In North America, three species of elapids are found, two species of coral snakes and one sea snake. The coral snakes are relatively small snakes that spend most of their time underground. Their primary food is other snakes. Despite their small size and small fangs, their venom is extremely toxic.

VIPERIDAE (vipers)

The vipers are generally considered to be the most advanced family of snakes since they possess a very sophisticated venom delivery system. Large tubular fangs are placed in the front of the mouth and they are hinged, allowing them to be folded back when not in use. Their heads are covered with numerous small scales and their eyes have vertically eliptical pupils. All the vipers found in North America are in the subfamily of pit vipers (Crotalinae) having a pair of heat sensing pits located between each eye and nostril. The rattlesnakes are a truly American family of pit vipers since they are not found in the Old World and all but two species are found in the U.S. or Mexico. They are divided between two genera based on their head scales. Members of the genus Crotalus have numerous small scales on their heads while members of the genus Sistrurus have large scales (plates) on their heads.