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Hundreds of tiny footprints left by mammals some 190 million years ago have been found on a canyon wall in a remote part of Dinosaur National Monument, which straddles the Utah-Colorado border.
The tracks are a rare find, mostly because they were left at a time when the area was a hostile, vast Sahara-like desert where towering sand dunes seldom preserved signs of animal life.
Most of the tracks are the size of a dime or smaller. A few include impressions of up to four toes. The mammals — perhaps the size of a rat — were able to survive between large sand dune fields where there was water, dinosaurs and a few plants. The Associated Press
