|MadSci Network: Evolution|
Hi Mark Good question, however as far as I know, nobody has really worked out the answer yet. The earliest fossil turtles found so far are from Germany and Thailand in rocks from the late Triassic period, about 225 million years ago. The oldest, called "Proganochelys", still had a few teeth as well as its beak but was otherwise similar to modern turtles with a full shell. As yet nobody has found an intermediate form to show exactly how turtles evolved, but other creatures with beaks instead of teeth existed too. During the late Permian period (250 million years ago), reptiles called "dicynodonts" also had beaks that they used to cut up the plants that were their food. So, maybe turtles developed beaks for the same reason - as an efficient feeding mechanism - but at present all we really know is that turtles came from an evolutionary branch of egg-laying animals in the late Carboniferous period about 300 million years ago, and then developed very differently from all other reptiles into the animals we see today. I hope that helps even though there is no definite answer - maybe someone will discover it soon. Yours, Dr David Hubble, UK References 1. The Book of Life - edited by Stephen Jay Gould, published by Hutchinson. 2. Vertebrate Life - by F. Pough, J. Heiser and W. McFarland, published by MacMillan
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