Robot used to show how Orobates walked

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A new study looked into the method of locomotion used by the diadectid genus Orobates pabsti, a close cousin to the last common ancestor of reptiles, dinosaurs, birds, and mammals and the oldest known creature for which we have found both well-preserved fossil skeletons and fossilized footprints. The study started by creating a 3D computer simulation of the animal's skeleton, which the researchers then programed to walk on models of the fossilized footprints while using different gaits. After 512 simulations, many gaits were found to be anatomically impossible, as they would have caused the animal's bones to clack against each other or caused its wrist joints to break. The model suggested that Orobates used a gait similar to that of a caiman, which hoists its torso into the air when it moves, a form of advanced locomotion that was thought to have evolved millions of years later after the emergence of amniotes. This suggests that the evolution of this method of advanced locomotion was not tied to the evolution of the egg. However, the simulation could not show the effects of certain factors, such as gravity, friction, and balance. In order to apply these factors, the team created a biometric robot, nicknamed OroBOT, and programed it to walk with several different gaits. OroBOT helped to rule out even more potential strides through various tweaks, such as how much the animal's spine bent as it moved, how wide its legs sprawled, and the range of motion found in its shoulder joints. After several trials, with some causing the robot to stumble and flip on its back and one actually resulting in the breaking of one of the model's ribs, the caiman-like gait was again deemed the most likely. This was backed up with similar tests involving digital skeleton models and footprints of salamanders and caimans, all of which produced gaits like those seen in nature. This study is significant because it helps paleontologists better understand when and why locomotion evolved in the way it did and may be an early step in understanding the way that early vertebrates moved from sea to land. Here is an image showing both the computer model and the OroBOT from the cover of Nature magazine, a video also by Nature that shows the model and the OroBOT in action, and a link to the paper describing this study.



Nature video: https://youtu.be/-Fz3JlGABrs

Paper (abstract only): https://www.nature.com/articles/s41586-018-0851-2