Around 350 million years ago, the first amphibious animals made their way onto land, and then some 40 million years later, the first amniotes emerged. A fossil excavated from central Germany’s Bromacker quarry in 2000 is thought to be a “stem amniote,” an early land-dwelling animal that evolved into today’s mammals, reptiles, and birds. The 290 million-year-old fossil is called Orabates Pabst, and it served a crucial role in determining how the creature walked.
John Nyakatura is an evolutionary biologist at Humboldt University in Berlin; he’s spent three years studying the ancient fossil, partly because it’s a “beautifully preserved and articulated skeleton,” according to him. The animal is intriguing for another reason, though, “because of its position on the tree of life,” related Nyakatura. Fossils from that period are especially informative in regards to the evolutionary changes that occurred and lead to further speciation, the process where populations become distinct species.
As the descendant of early amphibians, it was thought that the four-legged creature would kind of slither around on its belly as that type of swimming locomotion would have had many millions of years more to develop than that of walking on legs. But Nyakatura is not so presumptuous, so he partnered with robotics expert Kamilo Melo at the Swiss Federal Institute of Technology in Lausanne to investigate the creature’s gait. They modeled and 3D printed each bone and used motors to simulate muscles, creating a scaled-up robotic version of the animal called OroBOT.
Tracks of the creature have also been preserved in fossils so the researchers we able to use those as a guide, eliminating any gait that didn’t align with them. The motion model that best fit the tracks is one of an upright posture that’s more advanced than previously believed. “It walked with a fairly upright posture,” said Melo. “It didn’t drag its belly or tail.”
University of Maryland paleontologist Thomas Holtz, who did not participate in the study, said the research suggests “an upright stance goes further back than we originally thought.” 3D printing isn’t a time machine, but it does help us look into the past.