December 20 , 2016:

Two dinosaur trackways are present in the Upper Cretaceous (Santonian?) Crevasse Canyon Formation near Elephant Butte Reservoir in Sierra County. One is clearly ornithopod, but the other is too poorly preserved to be confidently assigned to a track maker. These are the first dinosaur tracks discovered in Sierra County and suggest more tracks may be found in the Crevasse Canyon Formation.

Spencer G. Lucas, Sebastian G. Dalman and Robert M. Sullivan (2016)
Cretaceous dinosaur footprints from Sierra County, New Mexico.
In Sullivan, R.M. and Lucas, S.G., eds., 2016, Fossil Record 5. New Mexico Museum of Natural History and Science Bulletin 74: 151-152