How turtles got shells, according to articles in ScienceDaily and ScienceShots 30 May 2013, and BBC News 31 May 2013 and Current Biology doi: 10.1016/j.cub.2013.05.003 30 May 2013. An international group of scientists have studied a South African fossil reptile named Eunotosaurus africanus and claim to have discovered how reptiles without shells evolved into turtles with shells. A turtle shell is a combination of broad flattened ribs, vertebrae and shoulder girdle bones. Eunotosaurus has nine pairs of broad flattened ribs and elongated vertebrae like a turtle, but the ribs and vertebral bones aren’t fully fused to form an external shell as in living turtles. It also does not have shell on its belly side, but has gastralia – belly ribs. Eunotosaurus, is dated as 260 million years old making it about 50 million years older than the oldest dated turtle. According to Tyler Lyson of Yale University. “Eunotosaurus neatly fills an approximately 30–55 million year gap in the turtle fossil record. There are several anatomical and developmental features that indicate Eunotosaurus is an early representative of the turtle lineage; however, its morphology is intermediate between the specialized shell found in modern turtles and primitive features found in other vertebrates. As such, Eunotosaurus helps bridge the morphological gap between turtles and other reptiles.”
Editorial Comment: This fossil was widely reported in many news sources, nearly all of them using a variation of the statement “How the turtle got its shell” for the headline. This is a good reminder that evolutionary stories are really like the classic “Just So” stories by Rudyard Kipling (1865-1936) which have the titles such as “How the Camel got its Hump” etc. Kipling’s stories are pure fantasy stories for children, but evolutionary theory uses the same mindset – an animal somehow acquired a new structure it didn’t have due to some outside agency acting on it. In Kipling’s stories it was a human being or a djinn (spirit). In evolution’s case it is the changing environment. However, change in the environment cannot produce the new genes required to give a living thing a new structure. Changing environments can only result in the death of creatures not already able to cope with the new environment. That is what natural selection does – it eliminates living things, it does not create new ones.
The fact that this creature had unusual ribs, and is now extinct, is no evidence that it is an “intermediate form” that turned into a turtle with ribs incorporated into a shell, or that it once had “normal” reptile ribs. No-one has observed an animal with normal reptile ribs change into one with the broad ribs seen in this fossil, so it does not explain how the turtle got its shell. (Ref. bones, reptiles)
Evidence News 12 June 2013