A well preserved turtle Skeleton showing how the plastron and carapace connect to the rest of the shell to form a complete shell covering the entire body. The skeleton (upper part) of the turtle is dissected to reveal the internal organs and respiratory system. In this specimen, the front part of the shell has been removed. Scales (left) and other skeletal elements (right) of the turtle’s carapace.
Over forty million years ago, a turtle fossil found in a French cave was a very old turtle. This ancient sea turtle had a very complete skeletal system including plastrons, ribs, vertebrae, skull and complete tail along with the original soft-shelled covering called keratin. Its close cousin the Eastern Rock Eel had a very similar rich marine life, which is believed to have given rise to the first land turtles. This discovery was made possible due to a special laboratory set up at the Laboratoire de l’ Archeologie in Tours, France.
This research team consists of specialists from the French and Italian Academie des Sciences and it is dedicated to finding out more about the sea Turtle called the Plankton. These scientists are working on finding out how the evolution of turtles took place through the slow process of shell evolution. The study is also trying to solve the question how did the shell evolve by using fossils and molecular biology. They are currently carrying out further research using techniques like molecular imaging to study the cellular level to study changes in gene expression and different cell types in the turtle’s shell over millions of years.
The study also involves looking into the physiological and behavioral differences between male and female eastern Carapaces. It is important that both sexes have the same shell composition and the same size, shape and color, with the difference being the fact that male Carapaces have relatively bigger plastrons, which is generally composed of two paired scutes. This is what is found inside the female’s shell. During the study both sexes will be placed inside the lab’s device and the difference between them will be determined. This way we can compare the two and find out which sex got the larger size and which one got the smaller one.
Another interesting part of this study is the comparison between the ribs and the scenes inside the shell. During the process of evolution, the ribs and the scutes were basically used as a sort of armor, with the ribs protecting the plastron of the turtle shell and the states acting as the teeth. However, some sort of evolution happened, and the ribs started to slowly protrude outwards. They even reached the tip of the turtle neck, which is when you see the ridges on the back of the turtle. This change came about because the two sides of the turtle’s body became paired, and because the evolution was occurring, the ribs and the states could no longer serve their original function.
After the Triassic period, which is about the second century of the Tertiary period, the development of turtles began to increase dramatically. The first evidence for such development was found in the form of small eggs, which were produced by the mating of a female with a male of the same species. This phenomenon is also known as convergent evolution. Evidence for such development can also be found in the mode limbs of some modern-day tortoise species, which are actually vestigial legs, due to the lack of an oppositional limb bone in this group of reptiles.
There is another type of evolution that took place during the latter part of the Tertiary period, and it is referred to as pyramiding. A type of marine iguana called the Squilla, with a relatively complete skeleton, possesses a number of patella and femur (the femur nearly forms a pentagonal stone), but none of the spinal column. It has been tentatively determined that these patellae occur due to the accumulation of bone fragments after the death of an adult tortoise, but this is not substantiated.
All throughout the evolution of tortoises, skeletons of mature adults have been discovered that bear clear similarities to that of sea turtles. However, when comparing the fossil record of the early Triassic to the fossils of modern-day tortoises, it is apparent that many differences between the two types of shells have been incorporated into the basic designs of the latter. Similarly, the modern occurrence of eggshells (or nautilus) in a sea turtle’s diet is clearly different from that of its ancestors. Without the appearance of these eggshells in tortoises, it is not possible to give a reasonable estimate as to how much food these animals ate.