The idea of any dinosaur, let alone the largest of them, tiptoeing around on "high heels" is almost too comical to be believed. However, new research suggests this was not only the case but possibly essential to their phenomenal size. Of course, these heels were inbuilt and more closely resembled running shoes than stilettos, but we can delight in the imagery anyway.

The study is the attempt of Andreas Jannel, a PhD student at the University of Queensland, to determine how large dinosaurs could walk given the immense forces they applied every time they put their foot down. Although some sauropods grew even bigger, Jannel focused his research on Rhoetosaurus brownei, which grew to 24 tonnes as the only known Australian Jurassic Era sauropod.

“Looking at the bones of the foot, it was clear Rhoetosaurus walked with an elevated heel, raising the question, how was its foot able to support the immense mass of this animal?” Jannel said in a statement. 

Elephants have a cushioned pad in their feet that stores energy as they walk, protecting the bones from strain and making it easier to take the next step. Jannel guessed sauropods had something similar, so he created replicas of Rhoetosaurus' footbones to work out the role such a pad might have played. His findings are published in the Journal of Morphology. 

Jannel acknowledged to IFLScience the exact height of the heel padding is unknown. He also has yet to explain why this method only applied to Rhoetosaurus' back feet – the front limbs appear to have laid flat on the ground. “We assume they carried more weight on their hind feet,” he told IFLScience, but added that the front feet would still have been carrying plenty.

Researchers haven't found many complete sets of footbones for large sauropods – none for Rheotosaurus' contemporaries elsewhere in the world, but Jannel has compared those we do have and used computer and physical models to fill in the gaps. By also examining their footprints, he concluded that Rhoetosaurus was not unique in this style of walking, and indeed it was probably universal among at least the larger members of the clade, suggesting it may have made their large size possible.

“There’s so much more to know, but it’s amazing to discover that becoming ‘high-heeled’ might have been an important step in the evolution of sauropod dinosaurs,” he said. 

The situation for other large dinosaurs, such as the big therapods that preyed on sauropods like these, is less clear. “We can see in some fossils they had a type of padding, maybe a little like an ostrich,” Jannel told IFLScience, but the studies are less advanced.