Prehistoric Trackways: Land Before Dinosaurs

By David Burge

Who needs a time machine, when a quick trip to the Robledo Mountains outside of Las Cruces can take you back millions of years in time?

Located about an hour’s drive from El Paso, Prehistoric Trackways National Monument contains world-class fossils dating back before even the dinosaurs walked the Earth.

The monument is located about 10 miles northwest of Las Cruces.

But a word of warning: Prehistoric Trackways can be difficult to find.

Even though it is just minutes outside of New Mexico’s second largest city, there are no signs leading your way in and very few signs inside the monument to guide your visit.

But for the enterprising visitor, you are rewarded with scenic views of desert landscape and about 30 miles of trails that can be used for hiking, mountain biking, horseback riding and even off-road vehicles.

But as the name suggests, the monument is really about the fossils it contains, but even these signature features are largely misunderstood.

Visitors often come expecting to see dinosaur bones or fossils, said monument paleontologist Colin Dunn.

“There are no dinosaurs, no dinosaur bones or dinosaur footprints,” Dunn said.  “It is all before the dinosaurs.”

What you can see — if you look carefully — are trace fossils dating back more than 280 million years.

Trace fossils document, in stone, the movements or behavior of animals, insects and marine life that once inhabited the area, Dunn said. They also include impressions of plants that lived millions of years ago too, he added.

“What you usually see are early conifer tree branch impressions,” Dunn said.  “Sometimes you will see petrified logs or pieces of petrified wood from those trees, footprints and tail drags from small salamander-like animals, footprints from small running lizards.”

The largest fossil you will see is about the size of your hand and is thought to be from the Dimetrodon, a mammal-like reptile easily recognizable by the large sail on its back, Dunn said.

You can also see spectacular examples of sedimentary formations like mud cracks, ripple marks and raindrop impressions.

The monument was created in 2009 by an act of Congress and is administered by the U.S. Bureau of Land Management.

“Of course, I’m biased, but we don’t have many opportunities to see these type of fossils,” Dunn said. “The preservation style is so great. You would have to travel a long ways to see something like this elsewhere and it is right here in our own backyard.”

You can explore Prehistoric Trackways on your own, but it’s recommended that you go on one of the free monthly guided hikes as an introduction.

On the third Saturday of the month, Dunn leads hikers out into the monument and walks them through the history, geology and paleontology of the area, giving a fun crash course.

His guided hikes only touch on a small part of the monument which contains more than 5,000 acres. But for the first-time visitor, the guided excursions are the perfect way to get a taste of what the monument has to offer.

“I do recommend that people come out on the guided hike,” Dunn said. “The tracks are fairly small and they are very easy to miss. When there is a guide that can point them out, you can really appreciate the value.”

Along the way, Dunn makes frequent stops to point out interesting features and to answer questions.

Two of out every three months, the guided hike goes out to the Discovery Site. That’s where Jerry MacDonald found the first significant slab or trackway of fossils in 1987.

This area had long been known for fossils, but MacDonald is largely credited with bringing national and international attention to the trackways.

The hike out to the Discovery Site is about a 3-mile round trip. The trail follows a natural arroyo, making for uneven and sometimes challenging terrain for hikers to traverse.

During the third month, the guided hike takes visitors out to the Site Flood area, where they can see petrified wood and fossils from marine life that have been discovered there. At one time, this area was under an ancient sea.

This hike, also about 3 miles round trip, contains several hills that may be challenging for some hikers.

Some of the trackways have been excavated to protect and study them. Some can be viewed at the Las Cruces Museum of Nature and Science, which serves as an unofficial visitors center for the monument.

Others have been transported to the New Mexico Museum of Natural History and Science in Albuquerque for safe keeping and further study.

Dunn said there are plans to add more interpretive signs at the monument and make improvements to some of the trails.

Make plans

Location: Prehistoric Trackways National Monument is about 10 miles northwest of Las Cruces, N.M. in the Robledo Mountains.

Directions: Take Interstate 25 north from Las Cruces. At the Dona Ana exit, take New Mexico Highway 320 west to N.M. 185. Then go north about a half mile to Shalem Colony Road. Turn west on Shalem Colony. Go about 1.25 miles and cross over the Rio Grande.

Take a right on Rocky Acres Trail. Go about a quarter mile and then turn left on the only dirt road, Permian Track Road.

Cost, hours: Free. Generally, the monument is always open but there are no developed facilities like restrooms.

Camping: There are no formal campsites, but dispersed camping is allowed.

Pets: Are allowed if on a leash.

Guided tours: Are held on the third Saturday of every month. They start at 9 a.m. October through April and then at 8 from May to September. Meet at the second parking lot in the monument.

Fossils: Leave only footprints and take only photos. Visitors are prohibited from taking fossils or other items with them.

Cautions: The hike to the Discovery Site goes through a natural arroyo. Watch for flash flooding during monsoon season. Rattlesnakes are also common.

What to bring: Lots of water, snacks, sunscreen and sturdy shoes.

Information: (575) 525-4300 or


Number 1 – Paleontologist Colin Dunn leads guided hikes out into the Prehistoric Trackways National Monument once a month. It is a great way to experience the monument for the first time.

Number 2 – Prehistoric Trackways National Monument contains some interesting examples of sedimentary structures and other geological processes at work.

Number 3 – Fossils found at Prehistoric Trackways include trace fossils of ancient plants.

Number 4 – Visitors can also see some spectacular examples of erosion and geological processes at work at Prehistoric Trackways.

Number 5 – At one time, Prehistoric Trackways was under an ancient sea. Here are two snail fossils found at the monument.

Number 6 – The largest fossil is about the size of your hand and is thought to be from Dimetrodon, a mammal-like reptile easily recognizable by the large sail on its back.

Number 7 – An ancient conifer tree is documented in this trace fossil found at Prehistoric Trackways.

Number 8 – Prehistoric Trackways is full of interesting fossils if you know what to look for. This is a fossil known as “Dromopus,” meaning “running foot,” left by a lizard-like creature.

Number 9 – The Prehistoric Trackways are located in the Robledo Mountains, which provide a scenic backdrop while exploring and looking for trace fossils.