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260-Million-Year-Old Pre-Reptile Walked Upright Like A Cow

Bunostegos akokanensis was about the size of a cow and ate vegetable matter.

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A study by scientists at Brown University has revealed that an animal that walked upright on four legs may be the first pre-reptile to roam the earth in such a manner.

Bunostegos akokanensis, a 260-million-year old pareiasaur was about the same size as a cow and stood upright on four legs. This is unique because the scientists who studied the fossils had expected it to have legs like that of some modern lizards, meaning the legs jutted out from the side of its body and slanted down from the elbow. It was the forelimbs on Bunostegos that convinced the researchers that it walked upright, like a cow. 


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"A lot of the animals that lived around the time had a similar upright or semi-upright hind limb posture, but what's interesting and special about Bunostegos is the forelimb, in that it's anatomy is sprawling-precluding and seemingly directed underneath its body–unlike anything else at the time," said Morgan Turner, the lead author of the study who is now a graduate student at Brown University. "The elements and features within the forelimb bones won't allow a sprawling posture. That is unique."

Taking into account the anatomy of Bunostegos, the researchers can visualize what the animal may have looked like.

Turner says that this upright posture may have been necessary for survival and that walking in this fashion on all fours was more energy-efficient than sprawling.  

“Posture, from sprawling to upright, is not black or white, but instead is a gradient of forms,” Turner said. “There are many complexities about the evolution of posture and locomotion we are working to better understand every day. The anatomy of Bunostegos is unexpected, illuminating, and tells us we still have much to learn.”