In 2021, Jonathan Charpentier was walking in a field behind his grandparents’ home in south Boulder when he spotted what appeared to be an especially shiny rock. Curious, the then 14-year-old pocketed it. Later, after he washed off the dirt, he compared the serrations on the curved mass to images of fossilized dinosaur teeth online; it looked enough like what he was seeing for him to email a photo to the Denver Museum of Nature & Science (DMNS).

Charpentier didn’t have to wait long for an answer. “They told me it was definitely a T. rex tooth,” he says. Although the original is now in the museum’s collection, he has a cast of the relic—and a story that should inspire dinosaur-loving Coloradans of all ages to look for signs of the creatures that roamed the Earth some 245 million to 66 million years ago. “It’s pretty crazy,” Charpentier says, “that you can find stuff like that right outside your house.”

Stumbling upon an exposed Tyrannosaurus rex chomper may be a rare occurrence, but uncovering fossils in the West isn’t. The dinosaur bone rush began in America in the 1870s, and ever since then, people have been pulling plant and animal remains from Colorado’s layers of sediment, which were conveniently uplifted during the formation of the Rocky Mountains. Unobscured by water or thick vegetation, local rock—from early quarries around Morrison and Cañon City to current dig sites in eastern Colorado’s Comanche National Grasslands and Corral Bluffs near Colorado Springs—has revealed countless discoveries that add to our understanding of ecosystems and evolution in the Mesozoic Era and beyond.

In recognition of the scientific value of that knowledge, in 2009, Congress passed the Paleontological Resources Preservation Act, which provided a framework and (some) funding for the protection of fossils on public lands. In the 1980s and ’90s, “you would come across pits where people had dug things out,” says Denver-based U.S. Forest Service national paleontologist Bruce Schumacher, one of just three paleontologists tasked with overseeing the Department of Agriculture–run agency’s 193 million acres, from Alaska to Florida. Even with official staff spread that thin, however, illegal pillaging by commercial collectors today is rare. The Forest Service credits the increased field presence of research teams—who hold permits issued by Schumacher and his counterparts at other federal agencies, such as the Bureau of Land Management—for the success of its fossil conservation efforts.

In Colorado, these legitimate fossil hunters are often groups of volunteers led by scientists from local organizations such as the DMNS. They mostly dig on remote public lands, but our fossil-friendly conditions mean that new construction in urban areas tends to turn up bones, too. “We’re always waiting for that phone call, because it is going to come every few years. The last one was 2019,” says Tyler Lyson, associate curator of vertebrate paleontology at the DMNS, referencing a triceratops that was uncovered in Highlands Ranch. “Usually, we get the picture and we say, ‘Well, it’s just a rock. It’s a cool rock. Keep the rock, treasure that rock.’ But then, every now and again, it’s something really, really cool.”

Collectors’ Items?

Pottery shards, arrowheads, and other archaeological artifacts on public lands have been protected for nearly 50 years, and such evidence of human activity should generally be left undisturbed. But federal law around collection of paleontological remains was only clarified relatively recently, in 2009, with a follow-up from the U.S. Department of the Interior this past summer. “It makes a distinction between kinds of fossils, particularly vertebrates,” U.S. Forest Service paleontologist Bruce Schumacher says. “It could be elephants, dinosaurs, ancient reptiles from before dinosaurs, fish, sharks—anything with bones and teeth are vertebrate animals and are protected.” So if you’re backpacking and come across something that looks like part of a prehistoric skeleton, snap some pictures, document the location, and share that information with a local museum, university, or public land manager. Those groups can then apply for permits to investigate and remove the fossils, which must be used for research or exhibition (i.e., not sold on the private market). Common plant, insect, and mollusk fossils, however, are fair game to collect in small quantities for your own enjoyment.

Discovery Zone

A three-part timeline of the Centennial State’s most significant dinosaur fossil finds and finders.

Prehistory

From the time humans enter what is now Colorado (by 11,500 BCE, though possibly earlier), they likely encounter fossilized teeth, bones, and tracks. The first records of such discoveries, however, come from more modern Indigenous peoples and their descendants. As noted in Stanford University historian Adrienne Mayor’s Fossil Legends of the First Americans, rock art and oral traditions centering on winged monsters and giant, primal beasts suggest that Native Americans across the West found remains and explained them, often via creation stories, over thousands of years. Navajo elders in the 1930s, Mayor writes, spoke of “places in the desert where one could see monstrous heads ‘sticking out from roots of trees and stones, from springs and swamps.’ ” Mayor also notes that in Delta, the Ute Council Tree, an important meeting place, stood just yards from a collection of distinct Jurassic theropod tracks.

The Bone Wars

1874: America’s intensely competitive rush on fossils—which involves bribery, sabotage, and a sense of urgency to name new species that often results in misidentifications—is heating up. Arthur Lakes, a teacher at a prep school in Golden who later becomes a professor at what is now the Colorado School of Mines (where the library bears his name), is hiking on South Table Mountain when his companion finds a large, serrated tooth. It’s eventually sent to Othniel Charles Marsh, one of the era’s leading paleontologists and Bone Wars protagonists, at Yale University, but it isn’t until 2000 that it is rediscovered in the Yale Peabody Museum’s collection and recognized as an early Tyrannosaurus rex fossil discovery.

1876-’77: Lakes, now working for Marsh—after sending remains to both him and his bitter Bone Wars rival, Edward Drinker Cope of Philadelphia, when Marsh was slow to respond—excavates in the Morrison Formation and documents the work in watercolor paintings. The fossil-rich rock unit (named after the Colorado town in the wake of Lakes’ discoveries) stretches from southern Canada to New Mexico and hosts six established dig sites, or quarries, in the Morrison area alone. There, the rock yields fossils Marsh uses to first describe the Allosaurus fragilis, Apatosaurus ajax, and Stegosaurus armatus. Meanwhile, in the prolific Garden Park area near southern Colorado’s Cañon City, a Marsh-backed hunter finds bones that help define the first described Diplodocus longus.

1887: Outside of Denver, George Lyman Cannon—Lakes’ former student and a high school geology teacher—finds a pair of horns attached to a skull that Marsh initially thinks is from a large bison but later uses to first describe the Triceratops alticornis.

1889: Cannon excavates remains near Denver that Marsh studies to first describe the Ornithomimus velox.

Modern Day

1993: The construction of Coors Field turns up dinosaur rib bones that are indeterminate but could be from a Triceratops—and thus, the Colorado Rockies’ mascot, Dinger, is born.

2017: While building a new police and fire department in Thornton, workers uncover what DMNS researchers at first believe are a Triceratops skull and partial skeleton. They turn out to be the most complete samples yet found of the rarer Torosaurus, which area elementary school students nickname Tiny.

2019: A large, adult Triceratops found during digging for a retirement community project in Highlands Ranch is estimated to be around 66 million years old, making it one of the last of its species to live before nonavian dinosaurs’ extinction.

A Prehistoric Field Guide

When dinosaurs ruled the Earth, Colorado looked a little different. This is what was flowing, growing, and roaming during the Centennial State’s most fossiliferous periods.

The Land

Although the Mesozoic Era—the age when dinosaurs lived—spans from 252 million to 66 million years ago, there’s not a lot in Colorado’s fossil record from the earliest period, called the Triassic, within that time frame. Why not? “The way I usually start this story is when the supercontinent Pangea begins to break apart,” Henry Fricke, a professor of geology at Colorado College, says. It’s a long story, involving huge land masses behaving like bumper cars and, crucially, high ocean levels that create the Western Interior Seaway, which floods the land that is now the Centennial State on and off over tens of millions of years.

“Whenever sea level is high and we’re underwater, that’s a bad time for dinosaurs, right?” Fricke says. When the water receded, however—particularly during later chunks of both the Jurassic (201 million to 145 million years ago) and Cretaceous (145 million to 66 million years ago) periods—the sludgy sediment left behind was ideal for capturing the animals and plants that flourished in the subtropical climate. “It would have been awesome,” Fricke says. “Mountains, then rivers, then an ocean; you could go skiing one day and go surfing the next.” Awesome, that is, until a six-mile-wide asteroid slammed into the Gulf of Mexico and wiped out 75 percent of life on Earth, including nonavian dinosaurs.

After that mass extinction event ended the giant reptiles’ 186-million-year reign, mammals began their rapid ascendancy, with Homo sapiens coming onto the scene around 250,000 to 200,000 years ago. Meanwhile, geologic and climatological forces shaped Colorado into the arid, exposed-rock-rich landscape that makes it such a fruitful place to find fossils today. “You had the right conditions for preserving fossils back then because you had all this sediment and water,” Fricke says. “Now we’re in the opposite sort of climate state; it’s much drier, there’s not as much vegetation, and rather than sediment being deposited in this part of the world, it’s being eroded.”

The Plants

Even if flora wasn’t present in the fossil record, we could surmise from the sheer size of herbivorous dinosaurs such as the sauropods that vegetation was thriving in Colorado during the Mesozoic Era. However, plant remains are so prevalent that people like Gussie Maccracken, assistant curator of paleobotany at the DMNS, devote their careers to searching for and studying them. This research informs the museum’s illustrations and dioramas (every leaf in the Prehistoric Journey exhibit is modeled off fossils from the appropriate time periods) and helps build fuller pictures of prehistoric ecosystems and the evolution of all species. “You’re thinking about, Who’s eating what? How is this food web structured?” Maccracken says. When we asked her what plants fueled Colorado’s dinos, she broke things down into two distinct categories.

Pre-Angiosperm

Today, 94 percent of described plant species on Earth are flowering varieties. In the late Jurassic period, the time most fossils in the Morrison Formation come from, however, angiosperms had not yet evolved. The forest then would have been made up of mosses, horsetails, ferns, cycads (which look like “short, stubby little palm trees,” Maccracken says), conifers, redwood trees, and ginkgos. “If you were to squint, you’d recognize the forms of things you’ve seen on Earth,” Maccracken says. “But if you looked closely at them, you’d feel like, Oh, well, obviously, this doesn’t grow in Colorado today. This doesn’t grow anywhere on Earth today.”

Post-Angiosperm

By the late Cretaceous— the age of the lower part of the Denver Formation that underlies the Mile High City area—angiosperms are present and “diversifying like crazy,” Maccracken says. “One of the things we think helps flowering plants dominate the Earth is that they can live in disrupted habitats. Along river channels, you could see lots of these newly evolved flowering plants, because when a flood comes through, they can pop up again really quickly. If you’re a redwood tree, you take a lot longer to grow.” Although nonangiosperms are still present, plants like laurels (relatives today include avocado and cinnamon trees) are abundant—and dinosaur diets are almost certainly changing to take advantage of the new food sources.

The Animals

From giant sea turtles to small marsupials, many creatures lived in what is now Colorado during the Mesozoic Era—but land dinosaurs have left the biggest imprints on our rocks and our imaginations.

Stegosaurus

Lived: Late Jurassic

Average Size: ~7.7 tons

With its upright ridge of diamond-shaped armor and spiky tail, the Stegosaurus—first described from remains found in Morrison—is a striking quadrupedal herbivore. In the late 1980s, new fossils from Cañon City helped paleontologists determine that its plates were staggered, rather than being in one straight row.

Allosaurus

Lived: Late Jurassic

Average Size: ~2.8 tons

One of the first discovered theropods (a class of bipedal predators), the Allosaurus would have been a common sight in what is now the American West. The majority of Allosaurus remains on the planet come from the Morrison Formation, which entombed many creatures and plants during late Jurassic period flooding.

Apatosaurus

Lived: Late Jurassic

Average Size: ~36.7 tons

This herbivorous, long-necked sauropod is the most abundant large dinosaur found in the Morrison area. There’s debate about whether the Brontosaurus is distinct from Apatosaurus, but they’re generally considered to be the same species, with Apatosaurus being the first name used and, thus, the scientifically preferred moniker.

Ornithomimus

Lived: Late Cretaceous

Average Size: ~400 pounds

A relatively small, birdlike theropod that may have been covered in feathers, the Ornithomimus was likely a swift runner that could have been omnivorous, using its toothless beak to feast on insects and lizards in addition to plants. It was first described by a partial hindlimb and forelimb that came out of the Denver Formation.

Triceratops

Lived: Late Cretaceous

Average Size: ~15 tons

Giant, three-horned skulls that could be up to a third of the length of its body characterize this herbivorous ceratopsian. Although rarer, remains of the closely related Torosaurus—with a larger frill that has two openings and sometimes reached nine feet long—have recently been uncovered in the Denver area.

Tyrannosaurus

Lived: Late Cretaceous

Average Size: ~8.5 tons

Perhaps the world’s most famous dinosaur despite its relatively short tenure on Earth, the carnivorous Tyrannosaurus likely scavenged and hunted prey (including juvenile ceratopsians and hadrosaurs, aka duck-billed dinosaurs) in the Centennial State during the late Cretaceous period, just before the extinction event.

Journey From the Crust of the Earth

How fossils make their ways out of regional rock shelves and into DMNS storage and exhibits.

1. Today, dig sites focused on finding organic remains of prehistoric life—such as bones, teeth, and soft tissue impressions (from animals and plants)—are usually selected one of two ways.

For the scheduled expeditions staffed by volunteers, interns, and visiting scientists the DMNS leads over some 20 weeks each year, it secures permits from land managers for sites—sometimes in Colorado, other times in Western locales such as Montana and the Dakotas—known to or suspected to hold fossils that could contribute to current research projects.

Other times, “things are prioritized because they’re opportunistic,” Salvador Bastien, a fossil preparator at the DMNS, says, citing the Ice Age mastodon and mammoth remains found during reservoir work near Snowmass Village in 2010. The DMNS moves quickly, mobilizing volunteers and borrowing construction equipment so as not to slow development.

2. Fossil hunters use whatever tools they can—from power drills and shovels to awls, chisels, and paintbrushes—to safely expose and stabilize the fossils. Then they wrap them, plus a lot of surrounding rock, with strips of burlap dipped in wet casting plaster to create casings called field jackets. Smaller items are hauled out in backpacks or on bodyboards, while tractors or even helicopters can be used for specimens such as a 13,000-pound Stegosaurus (on display at the DMNS) that was airlifted out of the Garden Park area near Cañon City by an Army Chinook in 1992.

3. Back at the DMNS, tall shelves in a second-floor storage area hold most of what’s been collected over the past decade or two—until the DMNS decides, based on museum needs and global requests, to crack the field jackets open in its labs, where fossils are prepped for display or study.

Part of the permanent Prehistoric Journey exhibit, the Schlessman Family Earth Sciences Laboratory is where most fossils are prepared by DMNS staff and 120-some volunteers. They use mini jackhammers, dental instruments, and sandblasters to painstakingly separate rock from bone; taxidermy putty fills cracks.

Larger field jackets—such as one holding the roughly 700-pound scapula of a sauropod from Comanche National Grassland that two DMNS interns worked on this past spring—go to bigger labs with garage door entrances that are part of the 63,000-square-foot, new-in-2014 Avenir Collections Center.

4. Once the fossils have been liberated, DMNS staff or outside experts occasionally make replicas that can be shipped off for research or exhibition. Unless the originals are being sent elsewhere on loan, they reside at the DMNS.

Only about one percent of the museum’s fossils ever make it to the exhibit floor. Those could be placed in cases or mounted (in combination with cast pieces to fill in missing bones) to create full skeletons. New hanging techniques are less damaging to the fossils than the old method of drilling holes in them, but the displays still pose challenges for scientists: “A couple of years ago, a researcher had to get up on a ladder next to the Diplodocus to study the bones,” Bastien says.

The rest of the DMNS’ two-million-some vertebrate fossils live in a brightly lit subterranean room under the museum. Protected, ideally, in custom-made fiberglass and plaster cradles, they’re placed inside towering, rolling white cabinets, where resident and visiting scientists can access them.

Hear Her Roar

DMNS chief fossil preparator Natalie Toth on being a woman in paleontology and digging up dino bones, including in Madagascar.

Growing up in Chicagoland, Natalie Toth wasn’t dinosaur-obsessed, but geology courses in college showed her a way to marry her love of science with being outdoors. Since she got her master’s in paleontology and started at the museum in 2017, she’s done just that, splitting her time between fieldwork and overseeing volunteers and staff who clean up fossils in the prep labs. Usually, you’ll find Toth digging in the West, but we caught up with her this past spring the night before she embarked on a four-week trip into the Madagascar backcountry with an international group of researchers.

5280: How do people get into paleontology?

Natalie Toth: I work with Salvador Bastien, whose background is in biology, and my background, geology, is another traditional pathway. Paleontology is the perfect combination of those fields.

What’s a common misconception you encounter?

People think all fossils have already been found, but the history of living organisms on Earth goes back three billion years. Every field season we go out, we’re still collecting new fossils, and not just dinosaurs, right? It’s dinosaurs and turtles and mammals and crocodiles, really everything from across the whole ecosystem—fossil plants, fossil fungi, all of it.

Tell us about your favorite part of your job.

I love the fieldwork. There’s something amazing about having a group of people who are off the grid, don’t have cell phones—all working toward a common goal. Then it’s really cool to watch interns or new volunteers have that same sense of wonder I had when I first picked up chunks of bone.

What will you be looking for in Madagascar?

We’re going to an area that has produced incredible meat-eating dinosaur fossils, crocodiles, fish—the entire vertebrate spectrum. Our main goal is to find fossil birds. Bird skeletons weigh just a few tens of grams, so it’s exceptionally rare to find them in the fossil record, but we have here. [We hope] the things we collect will help to inform the evolutionary pathway of birds we see in Colorado today. Of course, if we bump into other things, we’re not just going to leave them there.

Are there many women doing this work?

I’m the only woman from the United States on this trip, but there are women coming with us from the university in Madagascar’s capital. When I first got into paleontology, even going to professional conferences, I was hyper-aware of how few women there were. It has gotten exceptionally better over the last few years.

Plate Pride

Attention, dino stans: Soon, you’ll be able to rep Colorado’s state fossil on your ride.

While all but six U.S. states have a designated fossil, few are as, well, cool as Colorado’s: the Stegosaurus. (Arizona’s? Araucarioxylon arizonicum…a petrified conifer.) A little more than a century after remains from the Jurassic dinosaur were discovered on a hogback in Morrison, a fourth-grade class at Denver’s McElwain Elementary petitioned the governor to claim it for the Centennial State, and it was officially designated in 1982. This past May, the Stegosaurus State Fossil License Plate bill was signed by another governor, Jared Polis. The paleontological swag will be available from the Department of Motor Vehicles starting in January 2024; to get it, you’ll need to make a donation to Dinosaur Ridge, the nonprofit that manages the site where those original Stegosaurus bones were found. “Our state fossil invokes curiosity and wonder in people of all ages,” state Representative Brianna Titone, a bill sponsor and former geologist, says. “This bill will help inspire that scientific curiosity as well as preserve our fossils.” —Henry Carnell

Destination: Dinos

Eleven must-visit Colorado spots for prehistory enthusiasts. —Henry Carnell & Jessica LaRusso

Fruita

This relatively small institution pairs Western Slope fossils with robotic reconstructions and an impressive collection of seven life-size skeleton casts, many of which were made by Fruita resident and world-class restorer Robert Gaston (see “Finishing Touches” below).

Jensen, Utah

Although the showstopping Quarry Exhibit Hall—where you can view 1,500 late Jurassic fossils in a section of Morrison Formation rock—is technically in Utah, the 211,000-acre monument also spans northwestern portions of the Centennial State. Swing by Dinosaur, a nearby Colorado town where the streets are named after, you guessed it, dinosaurs.

Morrison

This near-Denver spot is famous for its tracksite. The 250 prints on a slanted slab of rock can be accessed for free along the two-mile (round trip) paved trail up a hogback northeast of Red Rocks Amphitheatre, and Dinosaur Ridge also offers paid, guided walking and bus tours and runs two nearby, kid-centric educational centers. About five miles north, the 1.5-mile (one way) Triceratops Trail, maintained by the same nonprofit, boasts tracks from late Cretaceous dinos.

Denver

The Mile High City’s nature and science museum is internationally recognized for its vertebrate paleontology research, which visitors can watch through windows into the Schlessman Family Earth Sciences Laboratory, where fossils are prepared. You can also just ooh and ahh at the Prehistoric Journey exhibit’s skeletons, including an 80-foot-long Diplodocus and battling Allosaurus and Stegosaurus.

Morrison

From the historical log cabin that houses this Morrison museum, you can see some of the hogbacks area resident Arthur Lakes excavated during the Bone Wars. Logically, its collection and research programs focus on regional finds. Included one-on-one guided tours will ensure you don’t miss Colorado bones that were used to first identify the Stegosaurus as well as rare juvenile tracks from the armored dinosaur.

Edwards

Billy Doran opened the Museum at Dinosaur Junction in June 2022 to showcase Eagle County finds: 80 percent of the fossils used to create his casts were unearthed within a few miles of the museum.

Woodland Park

A complement to Triebold Paleontology Inc.—which digs for bones, makes and sells skeleton casts to academics and institutions around the world, and creates traveling exhibits such as Darwin & Dinosaurs—this museum shows off the work of its parent company and also hosts shops that sell real and replica fossils.

Cañon City

The seven-year-old Royal Gorge Dinosaur Experience combines 12,800 square feet of exhibits—which hold fossils from the nearby Garden Park quarries (take the free-with-admission guided tour to learn more about the area’s Bone Wars history)—with a ropes course and a pea gravel pit where tots can dig for a T. rex cast. (Jurassic Park fans: Don’t miss the 15 life-size animatronic dinos outside!)

Cañon City

Located in the old Cañon City Municipal Building, this no-admission-fee institution southwest of Colorado Springs hosts rotating exhibits about the town as well as a fossil display with specimens from the area, which hosted the prolific, Bone Wars–era Marsh-Felch quarry in Garden Park. (Check out the fireplace, which incorporates dinosaur fossils, petrified wood, minerals, and part of a stalactite.)

Trinidad

No, there aren’t any obvious dinosaur remains at this park in southern Colorado. But if you follow the 0.75-mile (one way) Long’s Canyon Trail to outcroppings in its Trinidad K-Pg Boundary area, you can spot a strip of ash in the rock layers that documents the asteroid that struck Earth and wiped out our mighty friends.

Boulder

Inside the free, 121-year-old natural history museum on CU Boulder’s campus, the Paleontology Hall’s newest exhibit, The Dinosaur Freeway, opened in March and provides a deep look into Earth’s Cretaceous residents.

Finishing Touches

Fruita’s Robert Gaston is a global leader in fossil restoration.

Dinosaur skeletons are museum fan favorites for a reason: Nothing makes the giant beasts come to life like gazing up at a 15-foot-tall T. rex. But not every bone in those displays is a real fossil—and that’s where Robert Gaston comes in. “When you find a skeleton,” Gaston says, “typically, you’re finding 50 percent or less. The pieces you do find usually have a lot of damage.”

Gaston would know, because his Fruita studio is where institutions from across the region send their finds to be restored, whether that means sealing cracks in the real fossils or consulting with paleontologists to fill in missing bones. One of only a handful of people doing this kind of work in America, Gaston doesn’t charge museums for his services. Instead, he creates molds of the fossils and uses them to make reproductions he sells to collectors and other museums; the original finders get a cut of the proceeds, too.

It’s a gig he stumbled into more than three decades ago in the Utah backcountry. During summers off from college, Gaston was working for a Moab-area rock shop when he came across bones that appeared to be from an armored dinosaur. A paleontologist passing through the store thought they might be from an unidentified species, so Gaston led researchers to the site. It ultimately yielded multiple new specimens, including an Ankylosaurus dubbed Gastonia burgei.

Around the same time, Gaston met a Utah man who created molds and taught him the craft. At first, casting teeth and claws was a hobby, but 26 years ago, the sculpture major began working with fossils and making silicone molds and resin reproductions full time, employing crews of six to 12 people. “You never know what’s going to happen,” Gaston says, “and take your life in a different direction.”

See his work

In addition to many Colorado museums, the Weld County Administration Building boasts a fossil that’s gotten the Gaston treatment: In April, Pops the Triceratops, a 69-million-year-old skull found near Greeley in 1982, returned from a trip to Gaston’s shop.

Track Records

In southeastern Colorado’s Purgatoire River Canyon, you can stand in the footprints of Jurassic dinosaurs at North America’s largest tracksite.

Rumbling down a dirt road outside La Junta, cattle-dotted fields unfurl in every direction, but my eyes are searching for the canyon. We’d driven three hours from Denver and spent the night in a hotel to make the 8 a.m. start time of a full-day Picket Wire Canyonlands driving tour ($21 per adult, via recreation.gov). I’m ready for the adventure to begin.

Slowly, it does, as our caravan of four-wheel-drive vehicles moves through portions of Comanche National Grassland that are generally closed to automobile traffic. We angle our Toyota 4Runner around rocky outcrops and descend into the Purgatoire River Canyon. There are a couple of stops to view rock art that’s likely thousands of years old. Although the U.S. Forest Service guides’ interpretations are fascinating, we’re here to see something much more ancient: dinosaur prints left more than 150 million years ago.

Around midday, we park at the tracksite and follow the quarter-mile footpath down to the riverbank. At first, it’s hard to tell normal divots in the exposed rock from prints, but our guide points out three-toed Allosaurus indents and larger, deeper Apatosaurus tracks. As we take photos with our feet inside the impressions, a volunteer who helped with the excavations tells us about nicknames he has for their makers. Limpy’s gait gives away an injury, and Stucky, well, his tracks abruptly—and likely tragically—stop.

Too soon, it’s time to head back to the car to finish the tour. Wistfully, I watch mountain bikers who’ve arrived via the 5.6-mile (one way) path from the Withers Canyon trailhead. Now that I know what to look for, I think, next time, I’ll come on my own—and spend more time searching for meaning among the marks left by giants that wandered these grounds long before me. —Jessica LaRusso

Evolving Understandings

When dinosaur bones were first discovered, you could forgive their finders for being smitten with the larger-than-life creatures—and leaving behind whatever else was entombed in the rock. Today, however, the scientific community is interested in compiling a more complete prehistoric picture.

The Discovery

The University of Colorado Boulder’s Karen Chin published a study in 2017 on fossilized feces found in Utah, likely from late Cretaceous duck-billed hadrosaurs, which indicate they ate crustaceans along with plants.

What It Means

These dinosaurs, thought to be herbivores, may have consumed invertebrate-filled rotting wood for extra protein and calcium during egg-laying season—a diet-shifting behavior sometimes seen in modern birds.

Why It Matters

“It refines our diets of herbivorous dinosaurs,” Chin says. “So many of the dinosaur books show dinosaurs feeding on leaves of trees, and I’m sure many of them did. But natural history is more complex.”

The Discovery

In 2016, DMNS associate curator of vertebrate paleontology Tyler Lyson was inspired to search the Corral Bluffs landscape east of Colorado Springs for concretions instead of bones. The rocks, which form around organic nuclei and date to just after the mass dinosaur extinction, contained a previously overlooked trove of mammal skulls.

What It Means

The DMNS was able to lead a team that collected the world’s most complete record—some 1,000 vertebrate fossils, 6,000 plant fossils, and 37,000 pollen grains—of the era in which most of modern life emerged and diversified. (Note: The DMNS’ exhibit on the work, After the Asteroid, will close later this year.)

Why It Matters

“We found these amazing fossils in one of the most poorly understood intervals of time,” Lyson says. “It’s the first time that we can piece together four key things: the animals, plants, temperature, and then the timeline. We can really look at the recovery of a whole ecosystem.”

The Discovery

In 2007, Morrison Natural History Museum director and curator Matthew Mossbrucker noticed half-dollar-size, three-toed Stegosaur infant prints in a boulder pulled from a roadside near a historical quarry in the area.

What It Means

The herbivores were breeding in a spot with little plant evidence, supporting a hypothesis that they may have produced a substance like crop milk, which some modern birds secrete to feed their young.

Why It Matters

“Baby spike-tailed dinosaurs are rare,” Mossbrucker says, “and these tracks offer unique insight into the habitat where Stegosaurus grew up.”

The Discovery

Between 2014 and 2018, U.S. Forest Service paleontologist Bruce Schumacher led an excavation on the north bank of the Purgatoire River Canyon near La Junta that uncovered 800 Jurassic dinosaur tracks, bringing the area’s total to about 2,100.

What It Means

New parallel sauropod tracks of varying sizes (read: ages) bolstered previous interpretations that these herbivorous giants moved in herds, unlike carnivorous theropods, whose track patterns suggest they hunted alone.

Why It Matters

“The tracks capture actual behavior, as it happened,” Schumacher says. “Reflecting on the past makes us understand what a precious thing we have to preserve—our environment on Earth, not just for humans, but for all species.”

What Remains

How CU Boulder’s Karen Chin is studying the bodily waste dinosaurs left behind—and inspiring the next, more diverse generation of scientists via a children’s book out this month.

There are perhaps no two things more universally beloved by kids than dinosaurs and poop. So it makes sense that the work of Karen Chin, associate professor and curator of paleontology at the University of Colorado Boulder, is great fodder for juvenile nonfiction: The scientist, one of the world’s leading experts on fossilized feces (or coprolites), co-authored an elementary-level chapter book in 2005.

Much of her work has focused on what can be learned about dinosaur diets: If there is a snail in the coprolite, did the dinosaur definitely eat snails? (Nope; it likely slithered in afterward.) Do pieces of wood in a coprolite mean that dino ate trees? (Yes! Rotten wood was home to dinosaur delicacies like insects.) But her new picture book is just as much about how Chin—a woman of primarily African American and Chinese descent—came to work in a field where no one looked like her.

The Clues Are in the Poo: The Story of Dinosaur Scientist Karen Chin walks through her life experiences. Those include being inspired by her father, a member of the Tuskegee Airmen who later got a master’s degree in chemistry, as well as working as a rare woman ranger for the National Park Service in the early ’70s, when she first got interested in animal droppings while using them to teach visitors about modern animal behavior. “My hope is that the book will show that scientists, and people in any career, can come in many different flavors,” Chin says. The proof and inspiration for future generations, however, are in her work, which includes discoveries that changed the way we understand dinosaurs’ environments, diets, and more—all by studying their poop. —Henry Carnell

Dig In

Fossil work in the Centennial State is largely powered by citizen scientists. Here, four ways to become one of them. —Henry Carnell & Jessica LaRusso

At Denver’s pre-eminent dino institution, a devoted volunteer corps is entrusted with scraping sediment from previously collected bones and searching for new specimens. Following a two-day training, the museum asks for eight hours per week, and locals such as Don and Nikkie Brandborg—who’ve gone on 49 digs, from North Dakota to Cañon City—stick around for decades. “A lot of the people working here for free are some of the best preparators in the world,” DMNS preparator Salvador Bastien says.

For nearly 40 years, the Western Interior Paleontological Society has connected area dinosaur lovers. The group’s 400-plus members ($25 per year for individuals, $30 for families) nerd out together during meetings at the Colorado School of Mines, expert lectures, and multiday symposiums. They also go on field trips, such as behind-the-scenes museum tours, plant and marine animal fossil hunts, and paleontologist-led digs. For children ages seven and older, the organization hosts youth-specific PaleoZone programming.

If your kids blast They Might Be Giants’ “I Am a Paleontologist” on repeat (IYKYK), it may be time to send them into the field in Eagle County. “There are no screens,” Fossil Posse organizer Billy Doran says. “It’s just old school, get in the dirt and find fossils.” During the three-hour, $70 experience, offered on Wednesdays and Fridays from June through September, campers ages six and up get to make dino footprint casts and dig in a private quarry, where they may find shells, ammonite imprints, and shark teeth to take home.

This museum group offers prehistoric fun for the whole family on its two-day, full-day, and half-day excursions, starting at $115 per person. Hosted by Fruita’s Dinosaur Journey Museum, all programming features digging for fossils—finds are retained for education and research—and the longer options can include collections tours and learning how to use lab equipment to clean and repair fossils back at the museum.

This week, the American Museum of Natural History in New York will unveil its newest exhibit to the press: the skeleton of a huge plant-eating sauropod that many paleontologists think is the largest dinosaur ever discovered. The animal is new enough that it doesn’t yet have a proper scientific name — it’s being called Titanosaur for now. It is 122 feet long and 19 feet high at the midpoint of its back, a specimen so big that its head will peek out of the great hall of the Wallach Orientation Center and into the elevator bank on the fourth floor. Its dorsal vertebrae will brush the lofty ceiling.

But in the museum’s files is buried a description of a vertebra for a dinosaur that would have been 55 percent longer than the Titanosaur — and bigger than any animal ever known. The only problem: The vertebra described has been missing for more than 100 years, and many people think that it may never have existed at all, or at least not as it was described in the first place.

The missing dinosaur is known as Amphicoelias fragillimus, and the only recorded evidence of its existence — a piece of vertebra measuring almost 5 feet tall — is said to have been dug up just outside of Cañon City, a small town in central Colorado that for a few short years in the late 1800s was the dinosaur capital of the world. Along with dozens of bones from other dinosaurs, the partial vertebra is listed on the manifest of a freight train that went to Philadelphia, where it was first described and sketched in a paper by famed paleontologist Edward Drinker Cope. Around the time of Cope’s death in 1897, the Amphicoelias bone is said to have been sent with the rest of his massive collection to the American Museum of Natural History, where it was received and catalogued as FR 5777: “Amphicoelias fragillimus, Holotype.”

But when museum President Henry Osborn and his colleague Charles Mook finally got around to analyzing the collection more than two decades later, there was no Amphicoelias bone to catalog. In their exhaustive review of the sauropods of the Cope collection in January 1921, Osborn and Mook write, “The type of this species has not been found in the Cope Collection, and its characters cannot be clearly determined.”

It makes sense to be skeptical that an animal almost twice the length of a blue whale once roamed the American West.

A few months ago, I went searching for the truth about that missing bone. I was not the first — plenty of others have sought the largest dinosaur that has ever lived. What I found was a quest that has driven some people toward maniacal competition, some to conspiracy theories and others to disregard scientific consensus. It drove me to a little rocky outcropping on a hill in rural Colorado known as Cope’s Nipple.

My search started in Cañon City with Dan Grenard, a former Bureau of Land Management official turned amateur historian and paleontology enthusiast. Grenard is the kind of small-town resident who leads restoration projects, volunteers to share his knowledge with local middle-schoolers and knows pretty much everyone in the area.

When Grenard, a few others and I hiked into the hills behind Cañon City, we found the spot where Amphicoelias was likely uncovered. It was completely unremarkable. There was an ever-so-slight depression in the ground, and there were more light-colored rocks strewn about than in the surrounding areas. Melissa Smeins, who took over from Grenard as the Bureau of Land Management’s resident geologist, casually picked one up and handed it to me. “Dinosaur bone chip.”

Wait, what?

One hundred and thirty-eight years earlier, a seminarian-turned-teacher named Oramel Lucas had stood in the same spot — and also found bones. Lucas ran the one-room schoolhouse in the valley next to Fourmile Creek, which was a few miles north of Cañon City in an area now known as Garden Park. Lucas knew of other dinosaur digs going on in the area, but, as biologist Randy Moore writes in his book “Dinosaurs by the Decades,” Lucas may not have gone looking for them, instead simply stumbling across giant fossilized bones on a walk in the nearby hills. Whatever the provenance, he contacted one of his science professors at his alma mater, Oberlin College, who connected him to Cope. Lucas, it turned out, had wandered across a veritable Camarasaurus graveyard; over the next few years he’d pull six of these sauropods out of the 150-million-year-old green-and-red dirt layer in the hills known to geologists as the Morrison Formation.

Lucas’s biggest find, though, was yet to come. In 1878, Cope published a two-paragraph paper in The American Naturalist about it: “I have recently received from my indefatigable friend, Mr. O. W. Lucas, the almost entire neural arch of the vertebra of the largest saurian I have yet seen,” he wrote.

By that time Cañon City had changed. It had been a Western outpost where most townspeople worked as miners or shopkeepers and stagecoaches regularly rolled through the downtown strip bringing goods to the train station. In the 1870s, though, the cargo being transported shifted from ores to dinosaur bones as the town became ground zero for the growing rivalry between the two most famous men in paleontology: Cope and his rival, Othniel Charles Marsh.

This rivalry — now known as the Bone Wars — involved humiliation, bribery and eventually financial ruin for both sides. It also led to one of the most incredible periods of paleontological discovery in history, as the men’s rivalry led them to finance expeditions to the fossil bone beds of the West. Eventually, their teams identified more than 100 new dinosaur species, though many of those species have since been lumped together or otherwise revised. Amphicoelias fragillimus was one of the species discovered.

Marsh and Cope started out as friendly rivals, even naming new species after each other. Marsh was more academic and better funded — his millionaire uncle George Peabody built a museum at Yale for him — while Cope was more independent — he kept many of his favorite bones hanging in his Philadelphia house — and more prolific, cranking out more than a thousand academic papers. Cope eventually bought The American Naturalist to directly publish the notes on his finds. In Cope’s version of the story, their relationship soured when Marsh secretly bought bones from the workers at one of Cope’s quarries. In Marsh’s, the fallout happened after he publicly embarrassed Cope by pointing out that Cope’s Elasmosaurus reconstruction had its head literally coming out of its ass. Either way, the men went from sniping at each other to actively working against each other. At sites across the West, their workers were directed to sabotage one another, destroying rival camps, quarries and even bones.

Lucas’s findings didn’t go unnoticed by Marsh. As Lucas was shipping his first major haul out of the city, Marsh sent a Kansas professor named Benjamin Mudge to the area to persuade him to switch bosses. But Lucas was loyal to Cope, and thus the extremely large vertebra he found sticking out of the depression I was standing in was packed up and sent to Philadelphia.

One hundred and thirty-eight years later, I looked down at the rock Smeins had placed in my hand and saw that, yes — it was a dinosaur bone. There were little striations throughout the fossil, the telltale signs of carbon petrification. I looked around on the ground and there were little bits of dinosaur bone everywhere. Was I literally holding a piece of Amphicoelias in my hand? Who knows. As writer Brian Switek has explained, every paleo researcher is familiar with the feeling of finding a busted fossil. Where a beautiful bone once was, only unidentifiable fragments remain. Behold: the Chunkasaurus.

Grenard explained that the Amphicoelias probably existed a couple of million years after the other dinosaurs that were found there. That means that erosion exposed it first, and that many of the bones had likely shattered well before people could find them. Cope noted the thinning condition of the vertebra himself, calling the species fragillimus and noting that “much care was requisite to secure its preservation.”

Ken Carpenter, a short, stocky professor at Utah State University Eastern, spent 20 years trying to preserve something different: Cope’s discovery of Amphicoelias. In 2006, Carpenter tried to settle debate over the dinosaur by synthesizing his research in a paper titled “The Biggest of the Big.” It drew academic focus back to the dinosaur decades after it had been relegated to the sidelines.

For nearly two decades, Carpenter worked at the Denver Museum of Nature & Science, leading a team in charge of finding fossils. In 1992, while surveying the Garden Park area with his research assistant, he stumbled upon a huge find in a riverbank — a nearly intact Stegosaurus skeleton, one of the few that has been found.

The Stegosaurus made Carpenter a star in the paleontology world, but he was interested in an even more elusive quarry: Amphicoelias. He acknowledges that it’s most likely that the vertebra and any other Amphi bones have turned into Chunkasaurus, but he still spent years researching the animal and even more time combing the Colorado countryside looking for more Amphicoelias bones. When his traditional searches came up empty, he decided to bring in a ground-penetrating radar — generally used by excavation crews to make sure they don’t hit sewer lines — to see if he could find any bones still hiding under the surface. It was useless, since the fossils and rock matrix the bones are encased in turn out to have the same density. “It turns out it was nothing like ‘Jurassic Park,’” he says.

Carpenter, now 66 and silver-haired, was a little grumpy when I prodded him by phone about the big dinosaur; he says he has moved on from his monomaniacal pursuit of Amphicoelias. He now spends his field time looking for prehistoric mammals in northwestern Utah and calls the argument over the largest dinosaur a paleontological “dick-measuring contest” that he’s not interested in participating in. When I told him I may have been holding a piece of Amphi bone in my hand, he was unimpressed. “A bone fragment’s a bone fragment’s a bone fragment,” he says. But once I got him talking about his research into Amphi and the incredible lengths he went to to try to find more, he perked up and started getting excited, even wistful.

In his paper on Amphicoelias, Carpenter tried to synthesize everything known about the animal so far. He even reconstructed the missing bone out of plastic foam; after adding the missing parts, he had a vertebra that was more than 8.5 feet tall. Expanded along the dimensions of a Diplodocus skeleton, that results in an animal that’s 190 feet long. For comparison, blue whales can measure up to 100 feet long. “I’d like to model the entire skeleton,” he says. “But that’s still a pipe dream.”

ANIMAL LENGTH Amphicoelias fragillimus 190ft Titanosaur 122 Blue whale 98 Brontosaurus excelsus 72 Giant squid 59 Tyrannosarus rex 39 Triceratops horridus 26 African elephant 23 Stegosaurus stenops 21 Sources: Ken Carpenter, American Natural History Museum, The Princeton field guide to dinosaurs, national geographic

It makes sense to be skeptical that an animal almost twice the length of a blue whale — and more than 50 percent longer than any other known sauropod — once roamed the American West. For a long time, many in the paleontological world believed that it never existed at all, and that it was simply a fish tale Cope used to gain prestige in the ongoing battle with Marsh. But the fact that, as far as we know, Marsh never once took the opportunity to question the finding is instructive, as he would have loved to have more fodder to fight his rival. And although Osborn, director of the American Natural History Museum, bemoaned the missing bone in his survey of Cope’s collection, he was convinced it had existed.

Modern skeptics are less likely to believe that Amphi was fake than to believe that something else fishy was going on. Cary Woodruff is one such skeptic. He’s an adjunct instructor of earth sciences at Montana State University who specializes in studying sauropod vertebrae, and he’s not convinced that any dinosaur can get get much larger than 100 feet long. Early last year, in a paper titled “The Fragile Legacy of Amphicoelias fragillimus,” he and his co-author John Foster argue that not only is the Amphi bone likely just part of a Diplodocus specimen, it wasn’t even that big. Based on the other measurements in Cope’s notes — and the fact that Cope was notoriously careless in his rush to get out papers — they argue that the most likely explanation is that a typo changed the height of the vertebra from 1050 mm to 1500 mm, which would make it about a foot and a half shorter. “People have been working in the Morrison for 130-plus years, continuously,” Woodruff told me. “We have never found a single scrap of any other bone that’s even close to the size of what Amphicoelias is reported to be.”

Woodruff doesn’t think that Cope was trying to deceive anyone when he made his measurements, but that he realized soon after that his sizing was wrong. Woodruff’s theory? Cope wasn’t interested in being humiliated again as he was with Elasmosaurus, but he also didn’t want to perpetuate bad science. So he simply stopped talking about the great beast after his two-paragraph description in The American Naturalist. That would explain why Cope never mentioned Amphi in his later writings, even in his papers about evolution and larger body size that eventually became known as Cope’s Rule.

Carpenter disagrees, calling Woodruff’s theory of a cover-up a “pretty harsh accusation for a kid standing on the shoulder of a giant.”

And there’s another person who thinks the idea of a supersized sauropod may not be wrong out of hand: Nathan Myhrvold, the polymath CEO of Intellectual Ventures and former CTO of Microsoft. Myhrvold has recently turned his attention to dinosaur size. (In previous years, it’s been on cooking and nuclear power.) In a 2013 PLoS paper, he argues that most of our current size estimates of dinosaurs are wrong for two reasons: The first is that paleontologists aren’t great at using stats to approximate animal size from bone measurements. The second is that most of the individuals that scientists are using as prototypes for their species weren’t fully mature. “Unfortunately the specimens that have the most complete skeletons are not the very biggest ones,” Myhrvold told me over email. “I think that at some point we will find new specimens of enormous sauropod, and hopefully will have enough material to settle the matter. But even then, we may find scraps of something that might be even bigger.”

In the meantime, a small stream of large-dinosaur sleuths continue to make the trek to New York to see if there are any Amphicoelias clues at the American Museum of Natural History. Mark Norell, the current head of paleontology there, tells me that the big bone room was cleaned and recategorized eight years ago, so it’s impossible that the 5-foot-tall bone is in there. But he’s willing to leave a slight opening that it’s somewhere: “If you have a collection like ours — we’ve got nearly a million specimens — it’s like running a library. Things just disappear. Sometimes they show up years later.”

There’s a precedent for that. In 1998, a few amateur dinosaur hunters, including Jack McIntosh, a physics professor at Wesleyan who died last month, persuaded the museum to let them check out Cope’s files. Although Osborn and Mook had claimed there were no other records from the digs at Cañon City, McIntosh found several letters between Cope and Lucas, as well as Cope’s field notebook from a trip to Cañon City in 1879. In it was the first description of exactly where Amphi was found — Grenard and I used those notes to find the spot on Cope’s Nipple.

But those notes didn’t help us find more Amphicoelias specimens. So, after a long day out dinosaur hunting, I headed back to my hotel in Cañon City, the Quality Inn & Suites, and walked over to an alcove in the lobby next to the stairs. There, in the corner, was Carpenter’s reproduction of the Amphicoelias vertebra, mounted just like the other biggest dinosaur in the world, Titanosaur, minus a few hundred bones here and there. The model was too big to fit in his office, and the Denver Museum didn’t want it. So, thanks to a favor from a friend of Grenard’s who runs the hotel, it resides in the alcove, confusing tipsy guests on their way out of the bar for a smoke. It’s not the American Museum of Natural History, but for now, it will have to do.

CORRECTION (Jan. 11, 8:14 p.m.): An earlier version of this article misstated the tech company Nathan Myhrvold once worked for. He is the former CTO of Microsoft, not IBM.

You Can Both Swim and Hike on This Colorado Trail—It’s Summer Perfection

The Bear Creek Falls Trail Is One of the Best Waterfall Hikes in Colorado

Adventure’s Calling: This Trail Is Ideal for Discovering Dinosaur Fossils in Colorado

Oh, give me a home where the dinosaurs once roamed…yes, I know what you’re thinking: dinosaurs?! That’s right! Once upon a time, the Centennial State was a mecca for dinosaurs and other prehistoric creatures, and we have footprints and fossils to prove it! One such mystical site where dinosaurs once roamed is that of the Garden Park Fossil Area in Colorado:

Located in Canon City, the Garden Park Fossil Area is an extraordinary site with an equally remarkable history, both prehistoric and semi-modern.

Spanning 3,209 acres, the Garden Park Fossil Area has been the location of many dinosaur bone and fossil discoveries, including the first-ever uncovered remains of a Stegosaurus, Diplodocus, Ceratosaurus, and Camarasaurus.

If you think the discovery of these dinosaurs was exciting, you are correct; however, the story takes several strange turns, as two late 19th century paleontologists fought tooth and nail to find the most remains, resulting in the aptly-named “Bone Wars.”

As the story goes, the two paleontologists were so keen on making the biggest and best discoveries that they went out of their way to sabotage the other, which they did by sneaking spies into the others’ crew, bribery, and destroying previously prepared quarries.

While the paleontologists’ acts were unsavory, they weren’t without reward, as the area has turned out an incredible 136 new species!

Though you may not find too many fossils today, Garden Park is still worth a visit, thanks to not only the area’s history but also its resident wildlife, outdoor recreation opportunities, and unique camp spots.

To learn more about the Garden Park Fossil Area, please visit the Bureau of Land Management’s website.

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The Garden Park Fossil Area is open year-round and can be accessed from Canon City by taking Shelf Road north for 6 miles and pulling off at one of the marked interpretive signs.

Do you have a favorite place that you would like to see featured on Only in Colorado? Nominate it here! For even more to see and do in the area, check out A Terrifying Tour Of This Haunted Prison In Colorado Is Not For The Weak.