A 24-tonne dinosaur may have walked in a ‘high-heeled’ fashion, according toUniversity of Queensland research.
UQ PhD candidate Andréas Jannel and colleagues from UQ’s Dinosaur Lab analysedfossils of Australia’s only named Jurassic sauropod, Rhoetosaurus brownei,to better understand how such an enormous creature could support its own bodyweight.
“Looking at the bones of the foot, it was clear that Rhoetosaurus walkedwith an elevated heel, raising the question: how was its foot able to supportthe immense mass of this animal, up to 40 tonnes?” Mr Jannel said.
“Our research suggests that even though Rhoetosaurus stood on its tiptoes,the heel was cushioned by fleshy pad.”
“We see a similar thing in elephant feet, but this dinosaur was at least fivetimes as heavy as an elephant, so the forces involved are much greater.”
Mr Jannel and his colleagues arrived at this conclusion by creating a replicaof the fossil, and then physically manipulating it in an attempt to understandthe movement between bones.
“We also used 3D modelling techniques to assess the different foot posturesthat would have allowed Rhoetosaurus to support its weight,” he said.
“Finally, we looked at a range of sauropod footprints from around the world,many of which indicated the presence of a fleshy heel pad behind the toes,supporting what the bones were telling us.
“The addition of a cushioning pad that supports the raised heel appears to bea key innovation during the evolution of sauropods, and probably appeared inearly members of the group some time during the Early to Middle JurassicPeriods.
“The advantages of a soft tissue pad may have helped facilitate the trendtowards the enormous body sizes we see in these dinosaurs.”
The fossils of the specimen R. brownei were found near Roma in southwestQueensland and are dated to 160–170 million years ago, when Australia was partof the supercontinent of Gondwana.
Mr Jannel is now using computer techniques to simulate how different footpostures and the presence of a soft tissue pad affect stress distributionswithin the bones.
“In a nutshell, I’m using engineering tools to apply theoretical forces on thebones, assessing how stress is distributed within the feet of these giantdinosaurs, with the aim to provide mechanical evidence for the presence ofsuch a soft tissue pad.
“It can be a tedious and time-consuming process, but I’ve always beenfascinated by palaeontology, particularly the link between form and functionin extinct animals,” he said.
“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 sauropoddinosaurs.”
The research is published in the Journal of Morphology (DOI:10.1002/jmor.20989).
right hind foot of the fossil specimen of Rhoetosaurus brownei (QM F1659), indorsal view. The hind foot preserves the first four digits in completion, butis missing the fifth one. Credit: Jay P. Nair & Andréas Jannel.
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