I t is thought that snakes first appeared between 100 and 150 million years ago. No one knows exactly what the ancestors of snakes are, but it is assumed that it was some type of lizard that started to burrow into the ground, and eventually lost its legs because it didn't need them anymore.
Current opinion is that monitor lizards are the ancestors of snakes.
Snakes have gone through a long process that we only have fuzzy idea of. Colubridae is the largest family of snakes with an estimated 1,500 species. It is sort of lumped together, though undoubtably in the future it will be broken into smaller families. They have enlarged, grooved teeth at the back of the mouth connected directly to the venom glands. Even though this group of snakes are venomous, most are not harmful because of where their fangs are located and their venom is usually weak.