A team of scientists led by Yale University Professor Tyler Lyson claim to have filled in a 55-million year hole in the fossil record with their recent examination of Eunotosaurus, the first species to form the protective shell of modern turtles.
These turtles formed a "muscular sling which wraps around their lungs and organs to help them breathe" in exchange for added protection, explains Lyson. The 260 million year old Eunotosaurus allegedly served as the prototype for current day species.
The Yale professor adds "The reason, I think, that more animals don't form a shell via the broadening and eventually suturing together of the ribs is that the ribs of mammals and lizards are used to help ventilate the lungs. If you incorporate your ribs into a protective shell, then you have to find a new way to breathe!"
Animal Planet notes that the most ancient turtles date back 200,000,000 years, and are effectively the oldest known reptile group. Individual turtles can live up to 150 years-old, and "grow throughout life, although slowly after the first 5 to 10 years."
"Turtles are the only animals to form a shell that incorporates their ribs and vertebrae," says Lyson. "These bones broaden, and eventually the ribs suture together with other ribs and the vertebrae to form the major portion of the turtle shell."
"Eunotosaurus is a good transitional fossil which bridges the morphological gap between turtles and other reptiles," the doctor concludes.
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