It can be hard to picture a living, breathing creature based on just some dusty bones and old footprints, but paleontology is based on doing exactly that. Now that task might require a little less imagination, as researchers at EPFL and the Humboldt University of Berlin have built a robot to figure out just how a 300-million-year-old ancestor of ours might have moved around.

The animal in question is known as Orobates pabsti, which kind of looks like a big salamander. It sits at a crucial junction on the evolutionary tree, linking early amphibians to the reptiles and mammals that would follow. It also happens to be the oldest creature that scientists have been able to link fossilized bones with fossil footprints, making it the perfect target for this kind of study.

First, a team at Humboldt developed a digital simulation of how Orobates may have walked, based on what's known from its fossil skeletons and the sprawling gaits of similar modern animals, including caimans, salamanders, iguanas and skinks. The researchers took X-rays of these creatures as they walked, and examined three features in particular: how erect the animal stood, how its backbone bent, and how much its elbow and shoulder joints bent.

From that data, they had their virtual Orobates walk across a digital floor of its own footprints to see what kind of gait could have left them. The possible gaits in the simulation were limited to realistic ones – specifically, those where the animal's bones wouldn't have collided or popped out of their joints.

The next step was to bring this digital Orobates into the real world. The Biorobotics Laboratory at EPFL created the OroBOT, a creepy-looking robot version of the ancient critter. This one also has a customizable gait to test how the real Orobates may have gotten around. After identifying the most plausible gaits, the team had the OroBOT perform them and measured how much energy it took, how stable it was, how the leg forces lined up with similar modern animals, and of course how closely it matched the fossil footprints.

Orobates, it turns out, probably had a more upright swagger than salamanders or skinks. The team says the gaits that best matched all the above criteria were "quite athletic" and the modern animal it most closely resembled was the caiman, a small alligator relative. That tells the researchers that Orobates had a more advanced gait than was previously thought for its time.

The research was published in the journal Nature, and the OroBOT can be seen in action in the video below.

Source: EPFL