Nature & Environment

Fossil Reveals a Pre-Reptile That May be the Earliest Animal to Walk on All Fours

Catherine Griffin
First Posted: Sep 18, 2015 07:27 AM EDT

Scientists may have just discovered the earliest animal to have walked upright on all-fours. They've found the bones of a 260-million-year-old pre-reptile that tells them a little more about the process of ancient evolution.

The creature in this case is called Bunostegos akokanensis. It once roved the supercontinent of Pangea in the Permian era. Until now, though, researchers thought all the known pareiasaurs during that time were sprawlers whose limbs would just out from the side of the body-like some modern lizards. However, it seems as if this animal is different.

"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 its anatomy is sprawling-precluding and seemingly directed underneath its body-unlike anything else at the time," said Morgan Turner, lead author of the new study, in a news release. "The elements and features within the forelimb bones won't allow a sprawling posture. That is unique."

The animal was about the size of a cow, and stood in a similar manner. It at plants, had a knobbly skull and bony armor down its back.

In the past, the animal lived in Niger, which was an arid place at the time. Because water and plant sources may have been few and far between, it's likely that this animal had to travel between locations. This makes its upright posture far more energy efficient than a sprawling posture. In fact, this posture may have been necessary for its survival.

"Posture, from sprawling to upright, is not black or white, but instead is a gradient of forms," said Turner. "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."

The findings are published in the Journal of Vertebrate Paleontology.

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