Unknown ancient reptile roamed the Pyrenees mountains
Scientists say the new species is a member of the group that gave rise to crocodiles and dinosaurs.
The reptile lived at a time when the Earth was recovering from a mass extinction that wiped out most animals.
The discovery may shed light on how the group of animals evolved and spread.
About 252 million years ago, a mass extinction devastated life on land and in the oceans. Some 90% of species disappeared.
At the time, the Earth was very different from today, with continents grouped into the supercontinent, Pangaea.
Researchers led by Eudald Mujal of Universitat AutÚnoma de Barcelona, Spain, examined fossilised footprints from about 247 to 248 million years ago found in the Pyrenees mountains in Catalonia.
They found most tracks were made by the ancestors of crocodiles and dinosaurs, a group known as archosauromorphs.
Most footprints were small, about half a metre in length, although a few were longer than three metres.