"This is one of the most important sites ever found in New Mexico," said Spencer Lucas, paleontology curator at the New Mexico Museum of Natural History and Science.
The first footprint was found at the site in 1983 by Charles Pillmore, a surveyor for the U.S. Geological Survey, who died in 2003.
Lucas discovered the second print, and a partial print of a third, last month, The (Santa Fe) New Mexican reported Monday. The two full tracks show an impression of three toes and a dew claw, Lucas said.
The prints -- the world's only confirmed full T. rex tracks -- indicate a 6-foot-stride for a creature that weighed 6 tons and was 42-feet long from nose to tail tip with teeth the size of bananas, Lucas said.
"It was a very fast, very powerful animal," Lucas said. "It was a killing machine."