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.
“It’s just astonishing,” Dan Chure, a paleontologist at the monument, said Thursday. “We were giggling like kids.”
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He and paleontologist George Engelmann of the University of Nebraska at Omaha spotted the tracks July 8 while scouring the area for fossils and other evidence from the early Jurassic period. Dinosaur National Monument, founded because of its rich and plentiful supply of dinosaur bones, straddles the Utah-Colorado border.
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 among the few species that were able to survive between large sand dune fields where there was water, dinosaurs and a few plants, Chure said.