Amphibians have been using the same swimming technique for 270 million years, a set of ancient footprints reveals.
Massimo Bernardi at the Science Museum in Trento, Italy, and his colleagues recently found the fossilised tracks in the Italian Alps, in Permian rock deposits known to be between 270 and 283 million years old. The team reckon that the prints were made by an early amphibian around 10 centimetres long.
Impressions of entire feet can be seen in rock that was once under shallow water, but further into what was a lake only imprints of claw scratches and tail swishes are visible, suggesting the animal had launched into a swim.
The tracks are the first fossil record of an animal that old switching from walking to swimming, and reveal more about ancient animal movement than fossilised bones can, says Bernardi. "Tracks are very useful because they tell you about the life and activity of an animal," he says. "Instead of looking at a snapshot you see a movie."
The animal appears to have walked and swum just like modern salamanders, says team member Miriam Ashley-Ross at Wake Forest University in Winston-Salem, North Carolina. "Put newts down in the water, and they would make pretty much the same kind of trackway," she says.
Journal reference: Palaeogeography, Palaeoclimatology, Palaeoecology, DOI: 10.1016/j.palaeo.2014.05.032
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