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Terrestrial Adaptations of Reptiles

Reptiles evolved from amphibians during the late Carboniferous period, about 320 million years ago. The anapsids were the first to appear and they evolved into turtles and tortoises. They, in turn, gave rise to synapsid reptiles, which gave rise to mammals, and to the diapsid reptiles, the ancestors of modern lizards and snakes. Some reptiles, like plesiosaurs, lived exclusively in the water but they died out. Most modern lizards are now terrestrial.

A Shelled Egg
- Reptiles adapted to life on land by developing a shelled egg. This meant they could lay eggs on dry land, as amphibians usually could not, and their young didn't have to endure a larval stage. A baby reptile looked very much like his parents, but just grew larger and more mature. A reptile's egg, unlike a bird's, is leathery. It protects the embryo from drying out and being eaten. It also gave the baby time to develop, so when it hatched it was ready for life on land. Some reptiles now have their eggs remain inside the mother till they hatch, and the mother gives birth to live young. The young are still completely self sufficient.
Keeping Hydrated
- Turtles evolved separately from other reptiles.
  
  When the reptile hatched it had to be protected from drying out. The reptile then developed a horny layer that covered its scales or armor and prevented water loss. Reptiles, however, never solved the problem of being coldblooded, and must act to regulate their body temperature, either by moving around to heat up or resting in shade or water to cool down.
Breathing
- The reptile also had to breathe more efficiently than the amphibian. Amphibians force air in and out of their lungs by a throat pump, but reptiles breathe by expanding and contracting their rib cage, so air is sucked into the lungs and expelled. Thus, their breathing is dependent on the volume of their lungs and not the volume of their mouths.
Movement
- Most reptiles, like amphibians and fish, move by lateral flexion of their body, which means the body is twisted from side to side. The upper part of the reptile's limbs project from its body and its feet are angled a little to the side. Its toes are different sizes so that the weight of the body is shared equally between them. In most reptiles one of the ankle bones is hooked, to give greater leverage. All of this helped reptiles to successfully live on land.

Animals & Science