Sunday, October 26, 2008

The Evolution of the Turtle Shell

Part of the mystique of the turtle is that little is known about its origins. Did they evolve from dinosaurs, lizards, or do they stand alone as the only creatures adaptable enough to pass the test of time? Paleontologists have been clueless for centuries, but recently made a jump forward in knowledge with the discovery of a 210-million-year-old fossil, Chinlechelys tenertesta, in New Mexico. Years after the discovery of the first fragment, scientists Walter Joyce and Spencer Lucas feel they have solved the mystery of how the turtle got its shell.

The centuries old debate to explain the turtle’s unparalleled animal armor has two sides. Older theories pose that the shell developed from the ribs, which flattened and fused over time. Most modern scientists believe the shell was actually a separate material, hardened skin, which after years of evolution became fused with the rib bones. The fossil which was discovered appears to prove that the latter is true.

It took nearly 20 years of analysis and the discovery of many additional fragments before Lucas and Joyce identified their findings. Originally, they thought it to be a head spike from some sort of dinosaur, but after comparing it to a German collection of Triassic-era turtle fossils they knew the true significance of their discovery. Not only were they certain it was a turtle fossil, they could see on the underside of the shell that the rib bones and vertebrae were completely separate from the shell at that point in time.

You may be wondering how solving the mystery of the turtle’s shell gets us any closer to figuring out what creature it may have evolved from. First of all, it may help narrow down the search are for turtle fossils, as less than a dozen have been discovered in the world to date. Furthermore, it shows that although logic might say that such specimens would have survived as a whole, we now see that it could take many smaller pieces to compile one piece of turtle history. Lastly, I imagine there were many paleontologists ready to throw in the towel after nearly 200 years of searching for the next clue. Hopefully this momentous discovery has provided enough inspiration to renew the quest for turtle fossils throughout the world.

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