Fossil hunting 101: Lessons from a self-taught dinosaur tracker
“Do you want to hold a dinosaur?”
This is the chance I’ve been hoping for since I began covering science two years ago.
Scratch that: It’s the chance I’ve been hoping for since I was 4 and first watched “The Land Before Time.”
I reach out my hands. “Absolutely!”
Ray Stanford, a wiry 79-year-old with a slight Texas twang, passes me an oblong piece of reddish rock. He found it in a stream bed years ago, not far from an impression of a hatchling armored dinosaur now on display at the Smithsonian’s National Museum of Natural History. This stone has the same knobby appearance; Stanford says it’s the cast of a second baby, formed when the tiny creature drowned in a flood.
I cradle the fossil in both palms, savoring its heft, and try to imagine Maryland as this dinosaur might have known it more than 100 million years ago.
I can’t tell you where Stanford showed me his fossils. His collection numbers hundreds of artifacts and is worth thousands of dollars, keeping him extremely worried about thieves.
But I can say this: It’s an astonishing assemblage. There are perfectly round dinosaur eggs and weird-looking blobs of fossilized poop; footprints of creatures that could crush a person; tracks of primitive mammals so well-preserved that they might have been made yesterday by a raccoon. Though Stanford doesn’t have a college degree and has never taken a formal paleontology class, he is arguably the most successful fossil hunter in the Mid-Atlantic region. Thanks to his careful eye and dogged tracking, the number of dinosaur species known in Maryland has tripled.
When most people think of dinosaur fossils, they imagine femurs the size of cars and terrifying, toothy skulls. But Stanford’s specialty is paleoichnology - the study of the traces that ancient animals left behind, particularly tracks. A bone might tell you how an animal died, Stanford says, but its footprints show you how it lived. From faint impressions on ancient stone, scientists can divine whether an animal was walking or running, what direction it was headed, what other creatures it encountered along the way.
“When you study the tracks, and their action and interaction, you literally have the next best thing to a time machine,” Stanford says.
I’ve read enough science fiction to know that journeying back to the age of dinosaurs never ends well. But this form of time travel seemed safe enough.
So, on a recent sunny Saturday, I persuaded Stanford to share a few of his fossil-searching secrets. And now I’m sharing them with you.
1. Know your dinosaurs
Stanford might never have started hunting dinosaurs if his young son hadn’t stopped him in a bookstore decades ago and insisted on buying a copy of “Tracking Dinosaurs,” by Martin Lockley, a paleontologist at the University of Colorado at Denver.
At that time, few tracks had been found in their part of the country - but Stanford couldn’t convince his 11-year-old that searching would be pointless.
“I had no idea what I was getting into,” he recalls.
Not long after skimming through Lockley’s book, Stanford and his three children were walking in a stream in Maryland when they uncovered an unusual, three-lobed footprint in a broken piece of rock. “Daddy, it’s a dinosaur track,” the kids insisted. Stanford was more skeptical. But then, on a separate trip, he spotted what had to be the deep impression of a heavy sauropod.
“Wow,” he told himself. “I’ve got to get serious.”
To say that he succeeded would be an understatement. At one point, his living room contained so many rocks that his insurance company demanded that he install extra supports to keep the house from collapsing beneath their weight.
“But if I had not studied the literature about ancient finds, skeletal finds and footprint finds, I would not have known what I was finding and would have walked right over them without recognizing,” Stanford says.
Conveniently for aspiring trackers, many dinosaur groups are named for their feet. Large, long-necked dinosaurs like brachiosaurus and apatosaurus are called sauropods - literally, “lizard foot.” Their back footprints are typically large and round, topped by the scalloped impressions of toes, while the tracks of their front feet look like those of elephants.
The “beast-footed” theropods - a group that includes T. rex and velociraptor as well as the ancestors of modern birds - had V-shaped feet with three long, slender toes. Their tracks, if well preserved, often feature the sharp points of claws. The ornithopods, or “bird-footed” dinosaurs like the duck-billed hadrosaurs, also had three toes, but their prints tend to be wider and the outline of their feet more U-shaped.
Meanwhile, the prints of armored dinosaurs, like stegosaurus, are characterized by the arc of five blunt digits and the round impression of a “palm.”
Dinosaurs weren’t the only animals scurrying around 100 million years ago. Stanford also has found the webbed prints of pterosaurs - flying reptiles - and five-toed tracks from primitive mammals. Those can look like tiny hands.
One of Stanford’s greatest finds, an 8 1/2-foot sandstone slab uncovered at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, contains all of the above: tracks of herbivores and carnivores, reptiles and mammals, predators and prey, all intersecting and possibly interacting.
Lockley, now a friend of Stanford’s who helped him analyze the tracks for a paper published in the journal Scientific Reports, compared the 2012 discovery to the Rosetta Stone.
“A generation ago, people thought that tracks were nothing,” Lockley said when that discovery was announced in January. “They weren’t interesting; they weren’t the complete skeleton.”
But thanks in part to self-taught seekers like Stanford, “there’s been an absolutely huge renaissance,” he said. “Maryland is a really good example. Here we have a place where prior to the 1990s there were no fossil footprints at all, and then a guy who is an amateur, who is observant, goes out and he’s finding them in the middle of a high-security federal facility. ... This stuff is right at our feet, and we didn’t even know it was there.”
2. Know your geology
You can’t find dinosaur footprints if you don’t look in dinosaur-age rocks. This means any would-be paleoichnologist needs to figure out where to find exposed rock from the Triassic, Jurassic and Cretaceous periods - about 230 million to 66 million years ago.
First, get a good geologic map of your area (this interactive one from the U.S. Geological Survey is a personal favorite). Using the USGS tool, I can see in my region that rocks of the right age belong to the Patuxent Formation. This geologic formation contains rocks made of mostly sand, silt and clays that were deposited when eastern Maryland was a flat coastal plain, in the early Cretaceous.
But you also need stone that is good at preserving prints for millions of years. In the Washington area, the best stuff to seek out is ironstone, Stanford says. The iron in these 110-million-year-old reddish-brown rocks cements together grains of sand that once lined the wet banks of rivers, helping them maintain the shape of feet that stepped there millennia ago.
You don’t find fossils by digging or drilling into the ground. (In many places, this would be illegal.) So the best way to find a footprint is to look in areas where rocks are exposed. In Maryland, where much of the land is obscured by foliage or paved over with concrete, that means searching in streams.
3. Pay attention — but don’t get tunnel vision
After the visit to his fossil collection, Stanford and I head to the Northwest Branch of the Anacostia River in suburban Washington. We don knee-high waders and clamber down a steep slope.
The pace is leisurely, only partly because the path there is not maintained. Stanford keeps stopping to inspect things he sees out of the corner of his eye — a wildflower, an odd-looking seed. A turkey vulture wheels overhead.
“One of the few reasons a person would come down this way is to look for dinosaurs,” he notes. A second later, as if to prove his point, he gestures toward a clump of pointed leaves. “Watch out for poison ivy.”
Stanford trudges along the stone-strewn banks, his gaze intent on the ground.
“What are you looking for?” I ask. It’s the wrong question.
“The best way to keep yourself from finding anything is to keep yourself so goal-oriented,” Stanford chastises. “Go to have fun. Go to find and enjoy whatever is there.”
I nod, but I don’t think my editors are going to be impressed when I tell them I spent an entire workday learning to appreciate the moment.
So I pay careful attention as Stanford picks up and examines rocks. The ones that seem to hold his attention are rusty red — a sign of the oxidized iron within them. He ignores stones that have been made round and smooth by weathering, looking instead for flat, sharp-edged fragments recently broken from rocks upriver and washed downstream. If a track is going to be preserved, it must be pressed into wet mud, dried enough to solidify, then gently covered in a layer of sand or silt.
“And when it breaks out, it tends to be flat,” he explains.
Before our expedition, I imagined returning home triumphant, the clear print of an ancient animal in hand. Yet after about two hours of searching, though Stanford has filled a backpack with about 25 pounds of rocks, nothing we’ve found could definitively be called a track.
Still, something about these stones compels Stanford to keep them. He’ll hold on to the rocks for a few weeks or months and see whether any secrets reveal themselves when his mind is more relaxed. If not, he’ll return them to the spot from which they came.
Standing at the water’s edge, I notice a rock that is the same rust-red color. There’s a curved impression on one side — maybe a print?
I stoop and pry it from the mud, then hold it out to Stanford. Ignoring the mark that had caught my attention, he turns it over and points to knobbly structures on the other side.
“That’s kind of a nice specimen,” he says. “Looks a lot like feces.”
A hundred million years ago, a layer of mud might have covered the spot where a dinosaur did its business. Over time, minerals replaced the original organic matter, turning it into stone. That preserved poop — technically termed a coprolite — could be the lumpy rock I am now holding in my hand.
It’s not necessarily what I was hoping for. But I couldn’t be more delighted.