The Evolution & Ancestors of Snakes

Snakes are elongated, legless reptiles that can be found in most regions of the world other than areas where it is extremely cold. More than 2,700 different species of snakes exist. These animals can be found in forests, deserts, mountains, oceans and lakes. Although these creatures have existed for millions of years, the snake's evolutionary path is still largely unknown.

  1. Evolution of Snakes

    • Fossilized remains of snakes are rarely found, as snake skeletons are fragile and not easily fossilized. However, modern biologists have attempted to reconstruct an evolutionary history of snakes based on the evolutionary principle of natural selection, which dictates that more-desirable traits will eventually be bred into a species over time. Most paleontologists believe that reptiles evolved from a type of prehistoric amphibian called Labrynthodonts. This group evolved into two separate groups, amphibians and reptiles.

    Prehistoric Ancestors

    • The evolutionary trait that separates amphibians from reptiles was the latter's ability to lay a shelled egg on land, which freed reptiles from having to return to the water to reproduce. The oldest known fossil identified as a reptile is Hylonomus, found in petrified tree stumps in what is the modern Canadian province of Nova Scotia. Hylonomus was one of a group of ancient reptiles called Cotylosaurs, which also included Anapsids, Synapsids and Diapsids. The latter group eventually diversified into the now-extinct dinosaurs, as well as modern lizards and snakes.

    Spurs

    • As snakes and lizards split into different evolutionary paths, snakes eventually lost the need for legs. Certain species of snakes, however, still retain evidence of their earlier legged ancestors. For example, the Ball Python, native to western and central Africa, has "spurs," which appear to be like small claw-like protrusions on either side of its anal vent. In fact, these spurs actually are vestigial hind legs, a now-useless leftover from the snake's earlier evolutionary incarnation.

    A New Clue

    • According to a 2007 article in "National Geographic," the fossilized remains of a 95-million-year-old lizard may hold clues to how snakes came to evolve. The lizard, named Adriosaurus microbrachis (or "small-armed Adriosaurus") had a long, eel-like body, with normal-sized rear legs and far-smaller front legs. These front legs were vestigial, indicating this reptile may be something of a "missing link" between reptiles and snakes. Researchers who studied the fossil determined the lizard likely spent much of its time in the water.