According to a new digital reconstruction of sauropod dinosaurs' feet, a soft heel pad was important to their support.
Sauropods, which weighed up to 50 tons and dominated the world's ecosystems for around 100 million years, seem to have developed soft heel pads early in their evolution, and it was likely a key step that allowed sauropods to become the largest animals to have ever walked the earth
This week, our work appears in the journal.
The feet of sauropod dinosaurs are some of the biggest in the world, and they would have made a huge impact on the earth.
The name "brontosaurus" means "thunder lizard" in the language of sauropods.
The sauropods had long necks and tails, but they didn't start out big.
The ancestors of the dinosaurs were small, two-legged animals that were very similar to the theropods.
The estimated body mass of the sauropod ancestors was over one ton.
The largest sauropods, such as Argentinosaurus, Patagotitan, and Australotitan, reached adult sizes in excess of 50 tons more than the African elephant.
Animals of that size had large feet. The sauropod footprints found in Western Australia are large enough for most people to bathe in.
What did sauropod feet look like and how did they support their owners?
I have wondered what sauropods' feet would have looked like in the real world.
The front feet look like those of elephants, with the bones arranged in a semi-circular column, with the thumb missing. Most sauropod prints are rounded orbean-shaped.
The feet of sauropods were very different to those of elephants. The toes of sauropods were long and flexible.
The splay of the foot is not what we find in elephants today.
sauropods were thought to walk on their toes with the ankle joint elevated off the ground. Many sauropod tracks have the appearance of a large "heel"
Many paleontologists theorize that sauropods had aheel pads. The definitive evidence of a heel pad in sauropods has not changed.
We aim to change that.
Knowing what the foot skeleton of sauropods looked like, along with information about their tracks, made it possible for Andréas Jannel to figure out how their feet might have worked.
We collaborated with an expert in the foot mechanics of elephants.
The foot skeletons of various sauropods were created by Andréas. They used finite element analysis to test the strength of the models.
The mechanical behavior of the foot was compared with and without a soft-tissue pad.
None of the models could sustain the magnitude of mechanical forces that sauropods would have encountered in life, unless they also had a supporting cast.
Our findings show that a soft tissue pad would allow the foot skeleton to absorb the force of weight bearing.
The bones in the feet of sauropods would have crumbled under their weight if that pad hadn't been in place.
The Sauropods have traditionally been reconstructed as having walked with their toes slightly raised off the ground.
Our models show that the foot skeleton couldn't support their body weight without padding.
Evidence of pads behind the toes can be seen in some fossil tracks.
The "incipient" heel pad would be in line with our models.
The foundation for a more substantial structure was laid by the presence of an incipient heel pad in sauropods.
The first sauropods were over 10 metric tons by 170 million years ago.
Within 10 million to 15 million years, giant sauropods weighing more than 30 tons were walking the earth, and the diversity of giant sauropods began. The world would be dominated by them for 100 million years.
Steven W. Salisbury is an associate professor in the School of Biological Sciences at The University ofQueensland.
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