Check out these 3-toed dinosaur footprints in the Anapra Sandstone (Mojado Formation) of west Texas. I saw them on the field trip I went on there a year ago, led by Joshua Villalobos of El Paso Community College, on the northern flanks of the mountain Cristo Rey, an andesitic intrusion the same age and composition as the bedrock beneath UTEP’s campus. If you can’t make out the tracks, click on each photo for an annotated version.

Click for annotated version

Click for annotated version

Click for annotated version

Click for annotated version

I’ve arranged them here in order of least-jointed-stained to most-jointed-and-stained. The Anapra sandstone was fractured, and fluids flowed along those fractures to stain the joint walls with iron oxides, and soak some distance into the fractured blocks of rock, weathering them spherically to produced cross-sections with concentric gobstopper-like rings of rust:

Beautiful stuff. It’s a shame the dinosaur footprints mar this beautiful surface with their crude indentations… : )