File:Prehistoric-trackways-01.gif

Summary
Detail of a Paleozoic track in Prehistoric Trackways National Monument, New Mexico. Source

http://www.blm.gov/pgdata/etc/medialib/blm/nm/programs/recreation/rec_images/rec_images_las_cruces.Par.15762.Image.-1.-1.1.gif

Photo taken by government employee or official, and therefore released into the Public Domain. Oiginally uploaded onto Wikipedia.