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There are over 2900 known species of snakes in the world, and they make up fifteen families. To keep this blog-entry short and relatively simple, I will only discuss families containing more than 50 species.
Slithering Spaghetti
First is the family Leptotyphlopidae, which contains over 80 species. Commonly called Blind Snakes or Thread Snakes, all members of Leptotyphlopidae are fossorial and eat ants and termites. They are relatively small snakes. Very few species reach over 30 cm in length. Most grow to about 10 cm. These snakes are distinguished not only by  their size, but also by the fact that they have immovable top jaws and teeth only on the bottom jaw.
One species, Leptotyphlops dulcis, is found both in the ground and high up in the trees. These snakes were brought into the trees by predatory birds as food for their young. The snakes escaped by burrowing down into the nests and were able to sustain themselves on the insects living within the nests.
The smallest known snake in the world belongs to this family. Leptotyphlops carlae, discovered in June 2006, is said to be as thin as spaghetti. The largest recorded specimen is just over 10 cm (4 inches).
Big Boys
Next is the family Boidae, which contains over 60 species. Popular members of Boidae are boas, pythons and sand boas. In contrast to Leptotyphlopidae, Boidae includes the largest living snakes. Boid lengths range from under 50 cm (Exiliboa) to over 10 meters (Python reticulatus). They can be found in rain forests and dry tropical forests, mountain cloud forests and temperate coniferous forests, and in both sandy and rocky deserts. Boids may be terrestrial, arboreal, aquatic and semi-fossorial.
Many Boids have specialized infrared-sensitive pits. These pits are located near the mouth. They allow the snakes to accurately sense the radiant heat from surrounding objects and other animals.
Venomous Vipers
The Viperidae family has over 215 species. All vipers are venomous, and most have heat pits. They are also characterized by their hinged fangs. Most vipers can be identified by their stocky build and relatively short tail. Their scales are keeled (which means they have a ridge down the middle) and their heads, due to the location of the venom glands, have a very triangular shape. The pupils are vertically elliptical or slit-shaped and can be opened wide or closed almost completely, giving vipers the ability to see in a large range of light.
 For many people, the most familiar viper is the rattlesnake (genus Crotalus or Sistrurus). Its most distinguishing feature is its rattle, which consists of a modified tail tip called the button. The button is surrounded by other, modified scale segments that are added each time the snake sheds. This means that when a rattlesnake first comes out of its egg, it does not have a working rattle.
When a baby rattlesnake sheds for the first time, it gains its first additional rattle segment. A segment is added each time the snake sheds, which may be several times a year. Rattlesnakes will occasionally lose some or all of their rattles, but they can re-grow a rattle after a few sheds. Because the rattles are made of keratin (the material that comprises the external portion of the snake's scales, and human nails and hair), these rattles become softer and don't make any sound when they get too moist.
Editor's Note: Part 2 of this two-part series will run next week.
Other Blog Entries
New Animal Attractions
Reptiles: A Scaly Introduction
Snakes: They're All Around
Snakes: A Family Affair (Part 2)
Snakes: Clever And Deadly Behaviors
Snakes: Do The Locomotion (Part 1)
Snakes: Do The Locomotion (Part 2)
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Re: Snakes: A Family Affair (Part 1)
