A footprint is a strangely intimate fossil. A bone can describe an animal’s body after death. A trail of prints records a few moments while it was alive: a step into wet sediment, another step, perhaps a change of direction. In the Robledo Mountains northwest of Las Cruces, New Mexico, thousands of such moments survived from the Early Permian, roughly 280 million years ago. Some belong to early four-legged vertebrates, some to insects or other small animals. Plant impressions and petrified wood widen the scene. The land now looks like a dry, stony desert, yet the tracks formed near an ancient shallow seaway. Their survival is the reason the federal government established Prehistoric Trackways National Monument in 2009.
This is a worthwhile journey for someone who usually thinks of rockhounding as carrying a specimen home. Here the reward is seeing evidence in place and understanding the landscape that made it. The Bureau of Land Management’s current visitor page expressly says to observe and photograph the fossils without disturbing or removing them. It says collection of fossils, petrified wood, or minerals of any kind inside the monument requires a permit under the monument’s management plan. That site rule is stricter than the general casual collection allowance on some other BLM land. Treat the monument boundary and signs as controlling, and plan to leave with photographs, notes, and a better image of the ancient shore.
A desert ridge with an older shoreline inside it
Approaching the Robledos from Las Cruces, a visitor sees a range rising above the Rio Grande valley. Roads, irrigation, subdivisions, and the city belong to a recent human landscape. The rocks beneath the ridge contain a much older sequence. The BLM’s monument brochure describes this part of what became New Mexico as near the equator on the western edge of the supercontinent Pangea. A shallow tropical seaway lay nearby. Along its margins, water, mud, and sand repeatedly spread and retreated. Surfaces firm enough to hold a mark but soft enough to receive a foot were created, buried, and ultimately turned to stone.
That combination is rarer than the existence of animals. Most steps vanish at the next tide, storm, or drying and cracking of mud. Others are pressed into sediment but never covered in a way that protects the impression. At the trackways, a particular sequence of deposition and burial preserved enough detail for later investigators to distinguish tracks and sometimes behavior. The present outcrop is therefore only the last scene in a longer story: animal crosses a damp surface; new sediment covers it; layers harden; tectonic movement and erosion bring it back into view. A print that is visible today survived many opportunities to disappear.
The BLM describes footprints of amphibian-like early tetrapods, reptile-like animals, and stem mammals, as well as traces of insects and arachnids. These are broad descriptions of the ancient trackmakers, not a promise that every print can be assigned to one named species. A track is a trace fossil: it records activity. Bones and teeth, when available, provide different kinds of anatomical evidence. A large track may have been made by more than one possible animal with a similar foot. The sediment’s moisture, the depth of a step, and the way a foot was lifted can change the print. The first question beside a slab is what it actually preserves, not which dramatic creature to put in a caption.
The monument also protects plant material, petrified wood, and other fossils. Those remains make the scene more than a parade of feet. Plants occupied the surrounding land, washed into channels or were buried where they grew. Small animals left their own marks. The combination allows a paleontologist to ask how different organisms used the same shore and how conditions changed through time. A trackway gives direction and spacing; a leaf gives another glimpse of habitat; sedimentary structures show the water and ground beneath them. Taken together, they reveal an environment rather than an isolated curiosity.
Before dinosaurs, and before this desert
It helps to place the Early Permian on a human scale. The Permian preceded the Triassic, the period in which the first dinosaurs later appeared. It is not a chapter of dinosaur history just because it contains large and striking footprints. The BLM’s visitor page uses approximately 280 million years for the trackways; its older brochure describes an Early Permian setting around 286 million years. Those rounded public interpretations are close enough to place the site correctly, and neither should be presented as the exact birthday of an individual print. Geological dating and correlation work at the scale of rock units and intervals, not a calendar day when an animal crossed a tidal flat.
The climate and geography were also different. Today’s high-desert hike can be hot, dry, and windy. The ancient landscape included coastal flats and a tropical seaway. One of the most satisfying acts of imagination here is to stand in dry air and picture a moving shoreline crossing the same region. The ancient water did not simply turn into the present Rio Grande; the river valley has its own much later geological history. The fossils and the modern view belong to different chapters of a changing continent.
A single slab can contain multiple kinds of information. The direction of a series of impressions may suggest a travel path. The distance between alternating prints can say something about a gait, though exact speed estimates require careful assumptions. A set of tiny traces may reveal activity missed by someone searching only for a large, photogenic foot. Ripple marks and sediment layers can show the sort of surface crossed. These details are why a scientifically valuable slab should stay in context until specialists document it. A track cut from its bed and sold without its position loses part of the evidence that made it interesting.
How the trackways became a protected place
The landscape was known to people long before federal monument status. Scientific attention grew as the extent and variety of the track-bearing exposures became clear. The BLM’s visitor material identifies the Jerry MacDonald Paleozoic Trackways Collection at the New Mexico Museum of Natural History and Science as a home for selected specimens that were removed to protect and study them. The named collection is an important reminder that museum removal is a documented scientific act, not a casual precedent for taking a slab from a trail. A researcher records the context, receives authorization, and places the specimen where it can be examined by others.
Congress created Prehistoric Trackways National Monument on March 30, 2009. The BLM monument overview describes about 5,280 acres protected for paleontological, scientific, educational, scenic, and recreational values. The name puts the footprints first, but the protected landscape is wider than one celebrated bedding plane. It includes routes, canyons, outcrops, and the setting needed to understand them. It also means a visitor may be near valuable fossil material without a sign beside every specimen.
Protection has practical consequences. A track can be damaged by a vehicle, a boot scraping across its detail, a pet’s claws, an attempt to make a cast, or a well-meant effort to pry away loose rock. The BLM asks visitors to keep pets off fossil surfaces and to leave all fossil and mineral material in place without a permit. Federal protection keeps future researchers able to revisit a surface with better imaging and new questions. It also lets a family or school group encounter an ancient trace in the landscape where it formed, rather than only under glass.
The monument is managed by the BLM’s Las Cruces District Office. Some neighboring parcels are New Mexico State Trust Land, and the BLM overview warns that public use of those lands is governed by the State Land Office and requires its recreational access permit. Public ownership is not one uniform permission across the Robledos. Before leaving a marked route or planning a separate exploration, check an up-to-date land-status map. The absence of a fence does not establish that a parcel is BLM land, nor does a state permit override the monument’s fossil rule on federal ground.
A visit from Las Cruces
The current BLM directions start on Picacho Avenue/US 70 west of Las Cruces. Turn north on Shalem Colony Road for about 5.5 miles, west on Rocky Acres Trail, then left after about a quarter mile onto Permian Track Road. The final dirt-road stretch to the trailhead is roughly a mile. The BLM says the last mile calls for high clearance and may require four-wheel drive when wet; most passenger vehicles can reach the trailhead in dry conditions. Read that as a condition report and judgment call, not a guarantee for every car after every storm.
The trailhead has gravel parking. There are no toilets or drinking water on site, and cell service is limited or inconsistent. The trails are informal, rocky, and uneven, with washes and inclines. The BLM does not describe them as typically wheelchair accessible. The monument is open year-round with no entrance fee, but summer heat and sudden thunderstorms can change a pleasant walk into a difficult one. Spring and fall, or an early morning start, make more sense than a long midsummer afternoon. Carry more water than a short map distance might suggest, wear shoes suited to loose rock, and turn around while you still have enough daylight and water for the return.
The visitor page permits horseback riding, mountain biking, and off-highway vehicle travel only on designated routes. That restriction matters especially in a fossil landscape, where a shortcut can cut across an exposed bed or fragile slope. Hikers should use established paths and respect posted directions. Dogs may accompany visitors on leash, but should be kept off fossil surfaces. Primitive dispersed camping is allowed subject to current fire restrictions and posted instructions. The Las Cruces District Office, 575-525-4300, is the best source for a current route or closure question before a long drive.
A first-time visitor may expect a paved museum trail and a huge footprint highlighted at every turn. This is a rugged field setting. Slabs and impressions can take patience to recognize, and some important surfaces may be removed to museum care or remain unmarked for their protection. The outing is more rewarding if approached as a desert geology walk with a chance to recognize traces than as a hunt for a guaranteed single display. Take time to notice the bedding of the rock, the wash cutting through it, and the contrast between a mark on a surface and a crack running through it. Photograph what you find in place, including a wider view of the surrounding rock, without marking or wetting it.
Reading a mark without inventing its maker
A natural surface can deceive a hurried eye. Cracks, weather pits, root marks, and erosion may resemble toes. Conversely, a real track can be faint because later sediment pressed into it or erosion blurred its edge. When looking at a possible impression, examine whether it repeats at sensible intervals, whether the marks sit on the same bedding plane, and whether there is a consistent direction. Look for relationships among prints rather than a lone shape. Even then, leave formal identification to trained workers and published documentation. The pleasure of field observation does not require calling every hollow an extinct reptile’s foot.
Scale matters. A photograph without a ruler or familiar object can turn a small insect trace into something apparently enormous. At a protected site, put a scale beside a feature only if doing so will not touch or damage it; a notebook held off the surface may be enough for a personal record. Record the date, general area, and rock context. Do not post a newly noticed sensitive location with a precise coordinate if it might invite damage. Contact the BLM office if you find an unusual exposure or evidence that a protected surface is being harmed.
The difference between a body fossil and a trace fossil is useful here. A piece of petrified wood records material from an organism. A track records contact between organism and sediment. A burrow records activity below a surface. These can occur in the same succession but answer different questions. A slab with several track sets may tell a story of repeated use of a shoreline, while a plant impression helps characterize the surrounding ecosystem. This is why the museum collection and protected outcrops are complementary: one preserves detailed specimens for comparison, and the other keeps the wider field relationship legible.
An especially revealing question is whether a mark was made directly on the surface now exposed or whether it is a cast from the layer above. A foot can press down into mud, leaving a depression. Sediment deposited later may fill that depression; when the two layers separate, the filling can project as a raised form. Pressure can also deform layers below the surface actually walked. Thus two surfaces can carry related but differently shaped records of one step. A rounded bump is not automatically an animal’s raised foot, and a shallow hollow is not automatically the original footprint. The order of the beds and the way their surfaces fit together matter as much as the apparent outline. Looking at the slab’s edge, where it is naturally exposed, often teaches more than staring at its center. Do not split layers to test an idea: that destroys the relationship you are trying to understand.
There is a second reason to slow down. A series of prints may cross from one rock surface to another that has weathered away. What looks like an abrupt stop in the trackway can simply be a gap in preservation. A later crack may cut a print, and modern runoff can make the same mark look sharper after one storm and weaker after another. Field scientists document these changes through mapped photographs and repeated visits. A visitor can follow the same habit at a modest scale by photographing an entire surface before taking a close-up. The wider image preserves relationships that the most dramatic single footprint might hide.
The museums complete the field trip
The BLM says the New Mexico Museum of Natural History and Science in Albuquerque cares for selected trackway specimens in the Jerry MacDonald Paleozoic Trackways Collection. Its Geoscience Collection can be viewed by reserving a public tour, according to the current monument visitor page; confirm availability directly before traveling. A museum visit allows a closer look at scientifically conserved slabs and labels after a field walk has given their rock layers a physical setting. It is a good place to compare a questionable field impression with documented examples.
Closer to the monument, the Las Cruces Museum of Nature and Science displays two large trackways from the site, which the BLM describes as approximately 30 feet and 15 feet long. Their length makes the idea of movement visible in a way a single isolated print cannot. The museum display is particularly helpful for children and anyone whose hike is limited by road or trail conditions. It also answers a common disappointment: not seeing the most dramatic track slab in a canyon does not mean the landscape lacks a story. Some of its most informative evidence is protected and interpreted indoors.
The two settings ask different questions. In a museum, the viewer can see a conserved specimen, compare labels, and return to it in even light. Outside, the viewer notices how outcrops, washes, heat, and distance shape the work of finding and documenting a fossil. Neither replaces the other. A field walk without the museum may leave a visitor unsure what a real track looks like. A museum visit without the Robledos can make the slab seem disconnected from sediment, weather, and terrain. Together they show how a footprint becomes evidence.
Why this is a fossil destination, not a collecting site
General BLM rules sometimes allow limited personal collection of common invertebrate fossils or petrified wood from appropriate public land. The agency’s fossil collecting guidance also makes clear that vertebrate fossils and fossil trackways require a research permit. At Prehistoric Trackways National Monument, the site-specific visitor rule is broader: collection of petrified wood, fossils, or minerals of any kind is allowed only with a permit under the monument plan. A reader must apply the local rule rather than transplant a general allowance from another BLM tract. A piece that seems small or common can still carry information and remains protected within the monument.
There is also a distinction between looking at rock and altering it. Photography, sketching, and careful notes are ways to bring the experience home. Casting, scraping, digging, or breaking a slab changes the resource and falls outside ordinary visiting. If the goal is to collect a legal souvenir elsewhere, select a location whose land status and current rules have been confirmed separately. The Rockhound State Park chapter describes one posted, limited collecting opportunity near Deming. That park’s permission does not travel to a national monument.
The Robledo trip also helps distinguish fossil hunting from mining. Both activities depend on reading rocks, but a mineral deposit and a fossil bed preserve different histories. Near Apache Hill and Lake Valley, marine fossils in Mississippian limestone sit in a geological story that later includes silver-bearing fluids and mining. At the Robledos, the protected track surfaces are the reason for the journey. At Rockhound State Park, volcanic silica nodules are the focus. These places are not interchangeable stops on a generic “find rocks” itinerary; each asks a different question of the land.
An ancient crossing still visible
Imagine one wet margin before the sediment became stone. A small animal moves across it; a larger one crosses later; tiny invertebrates leave traces that a person might miss while watching the bigger prints. A new layer arrives before the marks are erased. Over immense time, burial, hardening, uplift, and erosion expose a portion of that old surface in the Robledo Mountains. The precise animals behind every mark are subjects of study. The larger story is secure: the dry hills preserve moments of life from a coastal world older than dinosaurs.
A thoughtful visit leaves the tracks where they can speak again. Walk the designated route, study the surface without touching or changing it, and make the museum part of the trip if you want to see large protected examples. The strongest souvenir is a more accurate sense of time: present-day Las Cruces below the ridge, Permian rock underfoot, and a few steps of ancient movement preserved between them.
Sources and trip planning
- BLM, Prehistoric Trackways National Monument visitor page: current access, roads, facilities, fossil and mineral collection rule, and museum information.
- BLM, monument overview: 2009 designation, extent, significance, and State Trust Land warning.
- BLM, monument brochure: Early Permian setting and trace-fossil interpretation.
- BLM, fossil collecting guidance: general categories and the permit requirement for fossil trackways; the monument’s site rule governs inside its boundary.