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 John R. Bolt, PhD
Geology Department
Curator, Fossil Amphibians and Reptiles
The origin and early evolution of tetrapods is one of the main research interests of vertebrate paleontologist John Bolt. Tetrapods are vertebrates with four limbs and digits, a category that includes humans. The earliest known tetrapods are from the Late Devonian, about 370 million years ago. Devonian tetrapods are found in fewer than a dozen localities, worldwide.
Tetrapod localities from the Mississippian, 354 to 323 million years ago, are also rare, with only about two dozen localities worldwide. Bolt is currently studying Mississippian tetrapods that he collected from a locality in southeastern Iowa. These specimens, plus those from a locality in West Virginia and another one in southern Illinois, represent all of the most productive Mississippian localities in the United States.
Preservation of many of these U.S. Mississippian specimens is very good, and in some cases exceptional. Preservation quality is particularly important in the case of the earliest tetrapods. These specimens have turned out to show many unexpected features, which would have been difficult to interpret from poorly preserved material. Taken together, the increasing numbers of specimens from the Devonian and Mississippian are finally beginning to give scientists a look at the first tetrapods.
Dr. John R. Bolt Interview
“The earliest tetrapods would have been expected to be primitive, and this has turned out to be the case. Nevertheless, something that has impressed me most about Mississippian and Devonian tetrapods is just how primitive they were.”
“Rather than looking at them as just very primitive tetrapods, it is often helpful to think of them as highly evolved sarcopterygian fish. But whether you view them from a fish perspective or a tetrapod perspective, one of the best things about studying early tetrapods is the way it forces you to change your expectations.”
 To find out how scientists trace the ancestry of today’s frogs and salamanders back to fossil tetrapods, take a look at the Dr. John R. Bolt Video created for the Evolving Planet exhibition.
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Continue to Dr. Peter Makovicky. >>
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