Vertebrate life began in the water, but around 340-360 million years ago, four-limbed creatures, or tetrapods, made the transition onto land. In the years that followed, some species adapted to terrestrial life, while others turned back to the water and readapted to an aquatic lifestyle.
A new study of these early amphibians, published in the journal PLOS ONE and led by Penn paleontologist Aja Carter, suggests that these environmental shifts left an impression–on the shape of the animals’ spines.
“I’m interested in how the shapes of the vertebrae affect how animals move,” she says. “Our findings suggest that, in at