|
Page 1 of 2
How snakes became what they are now
Snakes have been on this
planet for millions of years, and might be the most adapted of the
reptiles. We don't really know that much about how they developed
throughout the years (their skeletons are very fragile, so fossil
records are limited), but they probably appeared around the time of
dinosaurs, and descent from lizard ancestors alike the monitor lizard.
One of the oldest snake skeleton was found in the Saharan Desert, and
dates back to 130 million years ago.
The snake's ancestors was presumably aquatic at
first, but then they got the advantage that their eggs could be laid on
the ground thus making it possible for them to survive on land. A
process over millions of years caused them to become burrowers, and
this is probably when they lost their legs and external ear, making
them well adapted for burrowing. Their eyelids were replaced with a
clear scale, to protect them while digging. However, some biologists
believe that this happened while they were still aquatic, so there is
some controversy about this.
Millions of years later some of
these creatures emerged to the surface, and the snake as we know it
today was born. These snakes were in the boidae group, today's pythons
and boas, making these snakes the most primitive snake alive today. In
fact, pythons still have remains of their hind legs, called spurs that
stick out at the base of their tail. The boidaes have no venom, but use
constriction to kill their prey.
Around 40 million years ago,
smaller snakes appeared who had developed further, adapted to new areas
and created new characteristics, and these snakes became members of the
colubrid group, which is the biggest snake group today. Colubrids are
some of the snakes that are referred to as "New World" snakes. One
member of this family is the corn snake!
At first the snake world
was greatly dominated by the boidae, the colubrids were not able to
take over the areas of the much bigger python and boa. Then the world
went through a dramatic change, the temperatures got cooler, greatly
reducing the number of boidaes. They could not survive in the cooler
temperatures, which enabled the colubrids to spread over large areas,
as they got to be more temperature and climate tolerant then the
boidaes.
|
