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Scientists at the National Institute for Mathematical and Biological Synthesis (NIMBioS) at UT, along with scientists at Clemson University, have been watching tiger salamanders strut their stuff.

Scientists use the tiger salamander to investigate the stresses that early tetrapods experienced as they moved from water to land. (Credit: Todd Pierson)

It’s an exercise that’s helping them learn more about how the earliest four-legged vertebrate animals transitioned from water to land around 390 million years ago.

“How do we study the movements of animals that have been dead for hundreds of millions of years? One solution has been to study living animals that share similarities with fossilized animals of interest,” said Sandy Kawano, a postdoctoral fellow at NIMBioS.

Kawano was the lead author on the study.

The researchers used tiger salamanders to model the walking abilities of an early tetrapod because their anatomy and ecology are similar to those ancient creatures.

Bones must regularly withstand a variety of different forces, or loads, from both the contraction of muscles and interaction with the environment. Limb bones in particular must accommodate some of the highest forces.

Fossil records suggest that the forelimbs and hind limbs of ancient animals may have had different functions for walking on land, and the scientists wanted to learn more about this.

The researchers observed salamanders as they walked across a custom-built platform, which acted as a sophisticated digital scale that allowed the scientists to quantify how the animal accelerated and shifted its weight while walking.

“We used high-speed cameras to record these fine-scale movements of the salamanders as they walked over this device that recorded the forces that were being exerted onto the limb bones,” Kawano said.

The salamanders’ anatomy was studied and mathematical models were used to estimate how the limbs supported walking.

“Even though the limbs are about the same size, we found that the forelimbs had greater ability to withstand the physical demands of walking,” Kawano said. “These results offer new perspectives in modeling how tetrapods may have taken their first steps onto land, by considering the unique contributions of both the forelimbs and hind limbs.”

Hear researcher Sandy Kawano explain her research in this NIMBioS video.

 Watch the “salamander strut” in this NIMBioS video of a tiger salamander walking across the custom-built platform that measures the forces on the limb bones.



Sandy Kawano, NIMBioS, (865-974-4980,

Catherine Crawley, NIMBioS, (865-974-9350,