T. rex was a champion walker, super-efficient at lower speeds

While smaller dinosaurs needed speed, huge predators like T. rex were optimized for energy-efficient walking, according to a study published in PLOS ONE. Theropod dinosaurs included the dominant bipedal predators of the Mesozoic Era, and plenty of research has explored the relationship between their locomotion and lifestyle. Much of this work has focused on running speeds, but in a new study, Alexander Dececchi of Mount Marty College, South Dakota and colleagues argue that speed might not be the most important factor, especially for the biggest theropods. The authors gathered data on limb proportions, body mass, and gaits of more than 70 species of theropod dinosaurs. They then applied a variety of methods to estimate each dinosaur's top speed as well as how much energy they expended while moving around at more relaxed walking speeds. Among smaller to medium-sized species, longer legs appear to be an adaptation for faster running, in line with previous results. But for the real titans weighing over 1000kg, top running speed is limited by body size, so longer legs instead correlated with low-energy walking.