How sauropod dinosaurs, which include the largest animals that walked the Earth, were able to withstand the forces associated with their immense size represents one of the most challenging scenarios in the evolution of land-dwelling tetrapods. In new research, scientists in Australia used finite element analyses to quantify the biomechanical effects of foot skeletal postures with and without the presence of a soft tissue pad in five species of dinosaurs: Plateosaurus engelhardti, Rhoetosaurus brownei, Diplodocus carnegii, Camarasaurus sp., and Giraffatitan brancai; they found that none of the models can maintain bone stresses that fall within optimal bone safety factors in the absence of a soft tissue pad.
Jannel et al. suggest that a soft tissue pad in sauropods would have reduced bone stresses. Image credit: Andréas Jannel.
Sauropods, among the most iconic groups of dinosaurs, were originally believed to be semiaquatic animals that supported their gigantic size via water buoyancy.
However, the discovery of the first sauropod tracks in terrestrial deposits in the mid-20th century revealed their impressive land-dwelling abilities.
Yet, despite extensive research, one outstanding question persists: How did sauropods, and in particular their feet, support their gigantic body on terra firma?
“It had been thought sauropods had feet similar to a modern-day elephant,” said Dr. Olga Panagiotopoulou, a researcher in the Monash Biomedicine Discovery Institute at Monash University.
“Popular culture often depicts these behemoths with almost-cylindrical, thick, elephant-like feet.”
“But when it comes to their skeletal structure, elephants are actually ‘tip-toed’ on all four feet, whereas sauropods have different foot configurations in their front and back feet.”
“We found that the hind feet of sauropod had a soft tissue pad beneath the ‘heel,’ cushioning the foot to absorb their immense weight,” said Dr. Andréas Jannel, a researcher in the Museum für Naturkunde at the Leibniz-Institut für Evolutions- und Biodiversitätsforschung.
“We’ve finally confirmed a long-suspected idea and we provide, for the first time, biomechanical evidence that a soft tissue pad — particularly in their back feet — 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 own weight on land.”
“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,” Dr. Panagiotopoulou said.
“This was because sauropods and elephants had different evolutionary origins,” added Dr. Steve Salisbury, a researcher in the School of Biological Sciences at the University of Queensland.
“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.”
The study was published this month in the journal Science Advances.
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Andréas Jannel et al. 2022. Softening the steps to gigantism in sauropod dinosaurs through the evolution of a pedal pad. Science Advances 8 (32); doi: 10.1126/sciadv.abm8280
Source link: https://www.sci.news/paleontology/sauropod-soft-tissue-pads-11095.html
