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Cambridge University Science Magazine
Ripples are forming at the surface of a glass of water; scared children huddle at the back of a car; ominous footsteps resonate on the not-so-distant-anymore horizon. And suddenly, it appears: swinging its tail side-to-side, little arms tucked on the side, a T-rex makes its way into the frame, walking its characteristic walk. But how do we know which gait the now (thankfully) extinct giant adopted? Fossils can inform us on the position of limbs and the range of motion of articulations, and comparisons with extant species can give us hints about gait, but it is difficult to know how ancient species moved. Until now. In a new study published in Nature, researchers harnessed x-ray video, computer modelling and robotics to bring life to Orobates pabsti, a 280-million-year fossil that walked the Earth before any amniotes (creatures such as birds, reptiles and mammals) ever did. Based on well-preserved skeletons and studies of living reptiles, models were established of how this creature used to roam on land. Then an actual robot of Orobates pabsti was created: what model would make it walk into the (fossilised) footsteps of its ancestor? Different models were tested, and the ones that fit suggest that the creature had much more of an upright gait than expected for such an early land dweller. This may transform our understanding of how and when advanced styles of locomotion came to be.

Elsa Loissel is a feature editor at eLife in Cambridge. Image: Wikimedia Commons