A preserved turtle Skeleton showing how the plastron and carapace connect to the remainder of the skeletal structure to form a protective shell covering the entire body. The turtle shell is an extremely complex defensive shield for turtles (the Order Testudines) that completely envelops all of their internal organs and in particular the head, ventral portion of turtle. Although there are various other means of protecting a turtle’s body from the effects of space radiation and heat in space, the turtle shell has by far the greatest effectiveness, as well as a great degree of durability. For this reason the original turtle is preserved as a skeletal specimen to be studied closely.

The first known turtle Skeleton came from the Cretaceous geological period. It comprised of a hard, solid shell with an egg-shaped plastron. The egg-like plastron contained the sensitive reproductive organs. The shell covered the entire body of the turtle. There was no visible neck or head.

Another early type of turtle Skeleton came from the Jurassic period. The majority of Triassic specimens had complete legs, which were short with a tail, which did not have a true tale. They did however have flippers, which made swimming much more effective in the sub-tropical seas. From these fossils we know that the first turtles appeared in the oceans at least twenty million years ago.

There is more than just one type of turtle skeleton, so to speak. Each segment of the body corresponds to a bone or teeth. That is why you will notice segments with teeth or claws on each side of the Plastron. Also there are two sites along the lower back, also part of a turtle’s tail and body. These are flippers, or wings, that help the turtle propel itself through the water.

The basis for classifications begin with the plastron. The plastron is the top side of a turtle’s shell. It is the top portion that is exposed when the turtle is alive. It is composed of bony coverings and the teeth are generally located in front of it.

220 million years ago a small group of dinosaurs became the first source of nourishment for the ecosystem. They ate a variety of plants and stones, along with various types of shells and other items they found around their rock pools. The dinosaur fossils found in the limestone deposits of western Canada and southwestern United States are the source of much of what we know about today’s turtles and dinosaurs.

220 million years later, about a hundred million year ago, the dinosaurs became extinct. With these changes in the Earth’s environment, the need for a source of protein increased and so did the need for a more efficient way to digest food.

220 million years later the first turtles evolved from the same ancestor as previously mentioned. They developed a stronger shell (a plastron), developed their leg muscles to become wider and their neck to become longer and heavier to give them a more formidable look.

220 million years later, the first egg-laying reptiles evolved from the tiny ancestors that laid eggs to the largest known egg-laying creature ever recorded. This creature was called the Plio-cephalos. These creatures used their powerful jaws and sharp bite force to pull their eggs out of their female counterparts.

220 million years later, the first tracheal and gastralia were developed to aid the turtle in its aquatic lifestyle. The plastrons and gastralia formed into the first dorsal and ventral rib cage (DVCR) which are a paired cavity located behind the turtle’s head that supplies the turtle with both pulmonary and excretory functions.

220 million years later the first limbs were developed. At this point, the evolution of the turtle got underway and the first limbs were placed on the front of its head and the first tail became a hind limb like those placed on modern day turtles.

aldissacea evolved from a tracheal turtle and the first limbs evolved from the same. Throughout history, the evolution of turtles has been a remarkable story that has changed the course of history in more ways than we can imagine.

The stem- Turtle fossil record reveals that there were three types of turtles that are found together in the fossil record. The first two were called Cretaceous and Ordovician. The last one was a relative of both the Ordovician and Cretaceous as well as being a Mesozoic creature. The fossil record also reveals that both chordophores and the stem- Turtles lived together in the Eocene era.

All three types of turtles are classified as belonging to the Class Agammatophoridae which includes the stem-t Turtles, the lower jawed turtles and the arched back tortoises. The class Aridisks is comprised of such turtles as the African Agammatopard, the Barnecker and the Eastern Box Turtles. All these turtles have a long tail and are otherwise similar in features with regards to their skeletal development. The early Triassic period gave rise to the later Jurassic period with a transition zone between the prehistoric and the later Cretaceous eras. The transition zone involved many different types of turtle species which are reflected in the classification systems of today with the Stegoloma and the Parusita being among the first representatives of this class.