A preserved turtle Skeleton showing how the plastron and carapace connect to form the complete skeleton. Skeletons (upper) and ribs (lower) of a turtle are separated by a flexible band of skin, called the plastron. The turtle shell is an extremely complex defensive shield for the turtle’s entire body, protecting the ventral and dorsal portions of the turtle from the elements. In some species of turtle the entire plastron is encased within the shell.
The entire skeleton of a turtle can be seen along the inside of its shell by cutting a slit for a torch to pass through and exposing the inner tissues. In a few species, such as the leatherback turtle, the turtle skeleton is transparent and therefore appears as a white colored leatherback. In other species of this species the shell is colored inside and can even appear green or brown in places. A turtle skeleton is actually a series of bones arranged in a linear pattern inside of its shell. All of the bones are held together by ligaments and other tissues that keep the bones firmly in place and secure.
A complete turtle skeleton will consist of: ribs, sternum (neck), scapula (shoulder blade), ulnar (hip), diaphragm (heart) and diopters (kidney). The upper portion of the turtle body extends onto the lower back of the turtle and the lower back onto the tail. This arrangement allows for an incredible amount of movement within the turtle. The turtle can twist its whole body around to look at different things, such as underneath the tail, or under the ribs or even inside its shell. Its ability to twist is called cheilosis.
In order to fully understand the shape and movement of their bodies, it is necessary to look at the carapace, or shell. A carapace is simply a hard, heavy cover over the entire head and neck area of a turtle. Its size will vary greatly depending on what species of turtle is being examined.
All reptiles are descended from prehistoric creatures that walked on two legs. Over the course of millions of years, different species of reptile leg came together to create the modern-day varieties that we know of today. Modern reptiles have evolved into distinct species that have different characteristics common to all of them. One such characteristic is their shell. Each and every species of reptile have a special and beautiful shell that is unique to that species only.
The plastron is the top of a turtle’s shell. This is also where its paired claws are located. They are located between the eye and the lower jaw. Many people confuse plastrons with the osteoderma. Osteoderma is a thick, crumbly layer which is found alongside the asteroid.
If you were to view a typical plastron, you would see rows of hard, round shapes. These shapes, however, are not bones. They are actually sacs filled with fluid that help protect the inside of the plastrons. The plastrons have closed hollows in their interior, which keep the fluids inside from heating up and leaking out. This helps keep the inside of the plastrons cool even during warm summer months.
The fossil record shows us that dinosaurs appeared before us, over 100 million years ago, and that they used teeth to help break down tougher materials like coconut fiber. Over the last million years, different types of reptiles evolved and became the modern-day turtles we know today. There is no evidence that they used teeth, so we can safely assume that they did not possess them during the early Mesozoic era.
Throughout the history of sea turtles, there have been a few different types of shells. One of these shells was the egg-shell which has ten legs and could be used as a walking stick when needed. Theropods, dinosaurs who lived in the age between the Permian and Triassic eras, also had eggshell shells. The eggshell was lost only later on in the fossil record, along with many other pre-Caveman species. Since then, the eggshell has been replaced by an agamoid shell.
Modern day turtles range in size from twenty to eighty pounds and can live for up to a hundred and twenty years. They feed on fish, mollusks, crustaceans, and other aquatic invertebrates. A well-ornithized (preserved) fossil turtle shell would weigh in at around eight to twenty pounds in weight.
Turtle skeletal remains are usually located in two places: the anterior (where the neck and tail join) and the posterior (where they attach to the body). Sometimes they can be found in both places. They are buried in the sand, or even buried under layers of soil that is not washed away easily. Their soft undersides (the plastron and ribs) may also be partially visible. To preserve their soft bodies, turtles soak in saltwater or put them in an acrylic container to dry.
