National Geographic News:
The footprints are preserved in sediments in New Brunswick, Canada, that lay nearly a kilometer deeper than the oldest known (315 Ma) reptile bones—which suggests they were made by an animal that lived one to three million years earlier.
Howard Falcon-Lang from the U.K.'s University of Bristol said it was lucky that his team even found the fossil. The slab of rock had fallen from a remote stretch of sea cliffs, and a low sun shining across the surface cast revealing shadows.
Distinctive digits told the tale. Because the tracks showed five fingers and some evidence of scales, they had to have been made by a reptile, the team reports in a recent issue of the Journal of the Geological Society of London.