One of the most common mistakes made by beginner turtle keepers is confusing the difference between a turtle skeleton. Skeletons are simply dead bodies of a live turtle, which have been repaired in order to look like a dead turtle. Turtles lay their eggs inside of these Skeletons. Turtle Skeletons differ from a turtle shell in many respects, including size, shape, and color.

A turtle shell, on the other hand, is the living (but usually dead) turtle’s closest living relative. A preserved turtle skeleton demonstrating how the plastron and carapace connect to the remainder of its skeleton to form a protective shell enclosing the whole body. Plastrons (upper front surface) and carapaces (lower back surface) consist of many bones arranged in a manner which allows the turtle to move its head and neck freely and regenerate itself. The thickness and arrangement of the bones determine the shape and size of the turtle shell. The size of the shell, in turn, is related to the size and weight of the turtle.

The word “plastron” comes from the Latin word meaning shell. In a turtle skeleton, the upper portion or plastron is made of soft plasters and is attached to the end of the lower carapace by a series of grooves and channels. The channel arrangement of the channel provides a means for the turtle to push back or retract its head and neck. This action is powered partly by muscular activity and partly by a series of ligaments and muscles. The plastrons and the portions of the shell which surround them form the ribs of the turtle skeleton.

Although the origin of the turtle remains unknown, most research suggests that it evolved about two million years ago in the Middle East Sea (which is now known as the Cretaceous geological formation), before spreading out over the entire world. Estimates based on fossil evidence indicate that the first species of the modern turtle lived in the seas of what is now modern day Brazil approximately twenty five million years ago. It was later that these sea turtles evolved into the land turtles we know today, with the greatest diversity occurring in the Atlantic and Pacific Oceans. Estimates of the total number of sea turtles that inhabited the earth are uncertain because there is no evidence to support the age of fossils from more than one hundred years ago.

The plastron or the turtle skeleton consists of the following parts: the breast or the chest area including the nipple and the breast bone (the most important bone in the body); the sternum (the chest cavity); the diaphragm or the stomach; the colon or the large intestine; the uvula or the vocal cords; and the diaphragm or the rib cage. At the lower end of this skeletal frame there are two pairs of ribs or osteophytes. The upper half of the turtle body including the head, neck, legs, tail, and claws (beak and claws) is considered a plastron. In addition, the upper part of the turtle body is covered with small feathers called carotea, which serves as a protection for the muscles. These arrangements are believed to have originated around sixty million years ago in the Late Jurassic period.

Due to the extensive fossil record and the limited number of fossils that can be identified, it is impossible to determine exactly when the first turtle shell evolved. The most parsimonious theory is that the first bony plates that protected the body of the ancient reptile evolved and became the modern plastron. Phylogenetics proposes that the first bony plates (heloma) were derived from an ancestor of the modern day turtles. They were covered with scales and other hard or soft elements and evolved into the familiar modern turtle shell. There is also some evidence to suggest that the bony plates evolved first and were replaced by the softer plastrons that cover the modern turtle shell.

The fossil record does not provide clear evidence on when the modern turtle developed. Many believe that the dinosaurs became flightless sometime during the Cretaceous geological period. Others think that the earliest dinosaurs, which are thought to be the ancestors of today’s turtles, emerged during the Triassic period. In either event, the earliest known stem-t Turtle was a small theropod that possessed a very complex nervous system and a complex body shape that was nearly identical to that of its modern day descendants.

The most parsimonious hypothesis for the origin of the first turtle shell is that the ankylosaurids, a group of small marine reptile that are closely related to the dinosaurs, possessed shell. The ankylosaurids went on to become the ancestors of all later reptile species. Their enlarged jaws and powerful jaws allow them to consume large prey, including fish, and swim fast through water. The ankylosaurids gradually replaced their small terrestrial shells with bigger shells belonging to the Carboniferous family. The evolution of the turtle can thus be traced back to the rise of the Ceratoides.