Sauropods were the largest terrestrial animals that roamed the Earth for more than 100 million years. Among the most iconic groups of dinosaurs, they were initially believed to be semiaquatic animals that supported their gigantic size via water buoyancy. How sauropod dinosaurs could withstand the forces associated with their immense size represents one of the most challenging biomechanical scenarios in the evolution of terrestrial tetrapods, but also one lacking robust biomechanical testing.
Scientists from the University of Queensland and Monash University have cracked this enduring mystery. They discovered how sauropod dinosaurs – like Brontosaurus and Diplodocus – supported their gigantic bodies on land.
Using 3D modeling and engineering methods, scientists first reconstructed and tested the function of different sauropod foot bones. They found that the sauropod’s hind feet had a soft tissue pad beneath the ‘heel,’ cushioning the foot to support their immense size and weight.
Dr. Andréas Jannel, who conducted the research during his Ph.D. studies at UQ’s Dinosaur Lab, said, “We’ve finally confirmed a long-suspected idea and provided biomechanical evidence that a soft tissue pad would have played a crucial role in reducing locomotor pressures and bone stresses. It is mind-blowing to imagine that these giant creatures could have been able to support their weight on land.”
Monash University’s Dr. Olga Panagiotopoulou said it was thought sauropods had feet similar to a modern-day elephant.”
“Popular culture – think Jurassic Park or Walking with Dinosaurs – often depicts these behemoths with almost-cylindrical, thick, elephant-like feet.”
“But when it comes to their skeletal structure, elephants actually ‘tip-toed’ on all four feet, whereas sauropods have different foot configurations in their front and back feet. Sauropod’s front feet are more columnar-like, while they present more ‘wedge high heels at the back supported by a large soft tissue pad.”
UQ’s Associate Professor Steve Salisbury said, “this was because sauropods and elephants had different evolutionary origins. Elephants belong to an ancient order of mammals called proboscideans, which first appeared in Africa roughly 60 million years ago as small, nondescript herbivores.”
“In contrast, sauropods – whose ancestors first appeared 230 million years ago – are more closely related to birds.”
“They were agile, two-legged herbivores, and it was only later in their evolution that they walked on all fours.”
“Crucially, the transition to becoming the largest land animals to walk the earth seems to have involved the adaptation of a heel pad.”
Scientists are now planning to use 3D modeling and engineering methods to make further discoveries.
- Andreas Jannel et al. Softening the steps to gigantism in sauropod dinosaurs through the evolution of a pedal pad. Science Advances. 10 Aug 2022. Vol 8, Issue 32. DOI: 10.1126/sciadv.abm8280