One animal walked over fifty steps across this rock.
In nineteen eighty-seven, a man hiking alone outside Las Cruces, New Mexico, found rock full of trails like it.
His name was Jerry MacDonald, a self-taught fossil hunter. Over twenty-three years, he collected more than seven hundred slabs of footprints.
The rock is about two hundred and eighty million years old. Back then, this was wet ground beside a warm, shallow sea.
The most common prints are tiny. Under an inch long. The scientists who studied them say they look like a human baby's prints. Four fingers on the hand, five toes on the foot.
But in these hills, not one bone of the animals that made them has turned up. Only their footprints.
So scientists match the prints to feet found in other rocks. The baby prints belong to small, salamander-like amphibians. Long, thin toes belong to lizard-like reptiles.
And the fifty-step trail? Its foot matches a sail-backed hunter like Dimetrodon, the top predator here.
Scientists call these hills the most important early Permian footprint sites known.
In two thousand nine, Congress made five thousand two hundred and eighty acres of them a national monument.
One animal's fifty steps. One man's walk, alone in the hills. And now the hills themselves are a monument.
