From Ohio History Central
The first reptile appeared around 340 million years ago. These looked like some of the lizards of today. Because of their ability to lay eggs and adapt to living in a variety of habitats, reptiles survived, in one form or another, over the years. Today, there are four groups of reptiles in the world - turtles and tortoises, snakes and lizards, the crocodile family, and the tuatara (only two species of this ancient, lizard looking animals exists in the world). Ohio's reptiles include turtles, snakes and lizards. Reptiles usually hatch from eggs, looking like miniature adults of the species. Some reptiles, like Ohio's venomous snakes have eggs within their body, which hatch and come out as "live" young.
What's on the Outside?
The skin of a reptile is scaly which helps to keep in body moisture. This lets the reptile to live in dry environments, but it has a difficult time in keeping in body heat. Reptiles rely on the heat from their surroundings to warm themselves. This is where the term "cold-blooded" comes from. This warming process takes some time, which is why they are often found "sunbathing" on rocks and logs.
Reptile scales help to protect the body from drying out and damage by predators. These scales are just thickened skin made mainly of keratin, the same substance in fingernails. Most reptiles continue to grow throughout their lives. One of the growth processes in snakes and lizards is the shedding of its skin. Lizards shed their skin in large flakes a little at a time; snakes will lose their skin all at once. Snakes will shed their skin about 2 -3 times a year. Several days before this happens, the snake's eyes look cloudy, the skin looks dull, it loses its appetite and becomes more aggressive. When the snake is ready to shed, it will rub its head against the ground until the skin begins to turn back. It will then proceed to "crawl out of its skin," turning the old skin inside out. With a rattlesnake, this is the time when a new segment of rattle is added to the snake's tail. When shedding is complete, the snake's skin is bright and shiny.
What's on the Inside?
The teeth of a reptile do not wear down or permanently fall out when they get old. They simple shed their old teeth and grow new ones.
The skeleton of the Northern fence lizard is broad, providing stability and balance when it climbs a tree trunk. Fingers and toes are meant for grasping.
A turtle's shell is actually part of its skeleton. The carapace is made of two layers. Except for Ohio's softshell turtles, the outside of the upper shell is covered with plates, known as scutes. The inner layer is made of bone. Many of the bones, including the spine and ribs are fused to the shell. The turtles legs and neck are long and moveable. For protection, the head and neck can be tucked inside the shell when frightened. Some species of turtles, like the Eastern box turtle have a hinge on the plastron that allows them to close their shell up tightly for even better protection from predators.
The skeleton of a snake plays a major roll in its survival. The spine is very strong in order to handle the stress put on them by their powerful trunk muscles. These muscles are what move the snake along. Another partnership between the skeleton and muscles is in the jaws. After a snake has killed its prey, either by venomous bite or constricting, it is able to open its flexible jaws wide enough to swallow its meal headfirst and whole. This is possible by a special bone, which connects the lower jaw to the skull. The lower jaw can be stretched sideways with a ligament that's like a rubber band that keeps the two halves of the jaw together at the chin.
It's Not Polite to Stick Out Your Tongue
Do you know why a snake or lizard flicks its tongue in and out? It's not because it's rude - it's "tasting" the air! The forked tongue goes out and collects, or "tastes" particles in the air. It then pulls the tongue back inside its mouth and places it on the roof of its mouth onto special cells called the Jacobson's organ. Like a computer, the Jacobson's organ "reads" the information, which helps the snake or lizard find and follow prey, find a mate, know an enemy and find food.