Meet the Extinct Camels of North America, From Ice Age Giants to Sheep-Size Runners

Giant camels used to roam what’s now Los Angeles. If you visit the city’s La Brea asphalt seeps, you can see their bones, reconstructed into a massive skeleton gleaming beneath the museum lights. Paleontologists know the beast as Camelops, or “camel face,” the last of the largest North American camels.

Adult Camelops were truly imposing creatures. The biggest stood more than seven feet tall at the shoulder, a height that helped them pick vegetation from ancient forests alongside the mastodons, giant sloths and saber-toothed cats of their day. And they didn’t just live at La Brea. Several Camelops species roamed across North America for a span of three million years, ranging from the high Arctic to what is now Honduras. When Camelops ultimately vanished around 13,000 years ago, camels disappeared from the very continent where they had first originated.

Camels, as we know them today, no longer walk the wilds of North America. The two-humped Bactrian camel of Asia; the single-humped dromedary of Africa; and the llamas, guanacos, alpacas and vicuñas of South America are the sole surviving members of this diverse group of mammals. Tracing their 46-million-year history reveals the creatures have endured sweeping ecological changes. The story of camels is a tale not just of hungry herbivores browsing on shrubs, but of how life responds to Earth’s ever-changing ecosystems.

In broad evolutionary terms, today’s camels all belong to a group of herbivores called tylopods. The term means “padded feet,” for the cushioned, calloused two-toed feet that camels trot around on. Through more than a century of fossil collection and study, paleontologists have uncovered dozens of tylopod species from multiple continents. “There are around 100 extinct camelid species known from North America alone,” says Leibniz Institute for the Analysis of Biodiversity Change paleontologist Selina Viktor Robson. Combined with fossils from other continents, this makes camels among the best-represented of all land-dwelling hoofed mammals on the planet.

In fact, a century ago, experts had found so many different fossil camel species through multiple layers of rocks that they felt the series provided excellent evidence of evolutionary change. Since paleontologists had also uncovered a succession of fossil horses—showing their evolution from small, multi-toed herbivores to the large, one-toed forms we know today—the authors of the 1922 textbook General Biology noted “the history of the camel is accordingly as well established as that of the horse.”

However, camels never got the status of evolutionary icons that fossil horses have. “I think camels have gone overlooked for a few reasons,” says University of Calgary paleontologist Jessica Theodor, “the main one being that Europeans and settlers in North America were super horse-centric.” As domesticated pack animals, horses played a significant role in colonization, so their fossil backstory always garnered more attention than that of the camels that lived, evolved and ultimately went locally extinct alongside them.

“It’s a pity that the camelid fossil record has largely been ignored in favor of horses,” Robson says. They note that, like horses, North America’s camels “were key herbivores” in the era since dinosaurs’ extinction.

Robson, Theodor and their colleagues have been taking a new look at the evolution of camels, sorting out which species are related and how these herbivores changed with a world that’s become much more arid since the time of their origin. Early 20th-century paleontologists felt that they had a good handle on the evolution of camels and their relatives, but Robson points out that some previous identifications and assumptions require a fresh interpretation. “Tylopoda,” Robson says, “are absolutely bonkers when you get down to it.”

Part of the difficulty lies in the fact that previous generations of paleontologists treated tylopods as a wastebasket taxon—a group that puzzling fossils get tossed into for lack of a more precise identification. At the same time, misidentifications of other fossils led these paleontologists to assume that camels didn’t have much of a prehistoric tale to tell. But, Theodor notes, experts have likely collected more fossil camels than they’ve even realized. “In a lot of collections, camel skulls are mislabeled as horses, and if you aren’t looking for them, you’ll miss them,” she says.

Sorting through which fossils belonged to camel relatives and which have been misidentified is an ongoing task, but the outline of how small forest herbivores eventually evolved into the camelids we know today remains in focus.

As far as early camels are concerned, Robson says, “Poebrotherium is more or less the star taxon.” This sheep-size camel—about three feet tall—originated some 46 million years ago “and went absolutely wild,” they note, “proliferating like crazy.” The little herbivores were so numerous that they became staple prey items for the predators of their time. Fossils uncovered in Wyoming contain multiple Poebrotherium bones that were clearly munched on by a pig-like omnivore known as Archaeotherium.

Early camels like Poebrotherium lived in thick forests that flourished in a greenhouse world. Over time, however, Earth’s climate grew cooler and drier, favoring the spread of grasses that would eventually fill wide-open spaces between stands of forest. The soil of these grasslands was harder, favoring animals that could run quickly in open areas rather than hefty herbivores with spreading toes that were most at home in wet forests. Plant-eaters had to contend with greater amounts of grit, silica and other scratchy components of grass tugged out of the ground as well, meaning prehistoric horses, elephants and camels had to evolve their own solutions to abrasive food that wore down their teeth faster. Some herbivorous mammals, such as the rhino-like brontotheres, did not adapt to the changes and vanished entirely. But camels were among the survivors, changing as their ecosystems shifted beneath their two-toed feet.

Among the camels that flourished in increasingly open habitats was Stenomylus. These small camels stood about two feet tall and lived in North America between 16 million and 23 million years ago. “They were small-bodied creatures with gracile limbs,” Robson says, living in open habitats but browsing on gritty foods such as sedges and grasses among the wooded edges of open spaces. Stenomylus and their close relatives are often called “gazelle camels” for their resemblance to the unrelated small herbivores found in Africa today.

Based on their ancient anatomy, these camels appear to have been skilled runners that were suited to a world with more open habitat than dense forest. Many four-legged animals walk with a diagonal gait, with one foreleg on one side and one rear leg on the opposite side moving at once. But camels became leggy early in their history and adopted what’s known as a lateral gait, moving the front and back legs on the right side, for example, then both left legs together. “Lateral gaits have a higher efficiency because of long stride length but are less maneuverable in tight spaces,” Theodor notes, which means camels were better suited to moving in grasslands than in dense forests.

When forests opened, camels moved more comfortably and were able to adopt diets that involved both grazing and browsing. Camels essentially stood on the edges of these habitats, most at home where open spaces met patches of woodland with trees clustered together. “Camelids were already occupying open environments before grasslands spread,” Robson says, “and instead of evolving to have a predominately grass-based diet, they remained browsers and mixed feeders.”

At the same time as Stenomylus was running around, other camels evolved into a different niche. Oxydactylus overlapped in time, roaming North America between 13 million and 28 million years ago, but it was closer to a deer in stature. Even at this size, Oxydactylus had a very long neck, making it more like a miniature giraffe than a gazelle. The camel’s stature, as well as its extensive neck, enabled it to browse over a broader envelope of vegetation at the forest’s edge, allowing the camel to find enough food during a time when North America was rife with other herbivorous species all seeking to get enough salad to sustain themselves.

Of all fossil camels, though, perhaps none was stranger than Floridatragulus. This 18-million-year-old herbivore had an exceptionally long face and is called out by both Theodor and Robson as a favorite fossil species simply for how unusual it is compared to its relatives.

“There is not a lot of Floridatragulus material,” Robson says, “but from what we do have I can tell you that this camelid looked absolutely ridiculous.” The camel undoubtedly browsed on ancient plants, but its face vaguely resembles that of a giant anteater. The small canine teeth at the front of its jaws were typical for camels, but the length of its snout created an exceptionally large toothless gap in front of the grinding teeth. Why the camel had this dental setup is a mystery. No neck vertebrae have been found, so paleontologists can’t quite say whether this camel also had a long neck, Robson notes, but if it did, the neck “was most likely used for reaching otherwise inaccessible vegetation.”

From gazelle-like runners to long-faced enigmas like Floridatragulus that Robson calls the “problem children” of the group’s family tree, camels flourished in North America for millions of years. And, as we know from our modern vantage point, they didn’t stay put.

As continents shifted and sea levels changed with the climate, new connections and land bridges opened. Around seven million years ago, giant camels related to today’s largest camels lived in high Arctic habitats in North America. Based on their teeth, these camels plucked needle-packed branches from conifers in the prehistoric taiga. When a new land connection opened with what’s now Russia, camels moved across and dispersed through the continent, eventually evolving into the dromedary and Bactrian camels of Africa and Asia today.

A similar phenomenon took place around three million years ago when a firm land bridge formed between the northern and southern parts of the Americas via the isthmus of Panama. Creatures from South America, like armadillos and giant sloths, moved north, while North American mammals, such as the ancestors of jaguars, maned wolves and llamas, moved south. North America was the crucible of camel evolution, but the herbivores wandered to other landmasses as they opened.

The reason why camels have persisted elsewhere in the world but not where they originated remains contentious. North America’s camels, like the giant Camelops, had entirely vanished by 13,000 years ago. Even though Pleistocene people hunted camels, this alone didn’t drive them to extinction—paleontologists working at La Brea and elsewhere have begun to find a more complex picture. In what’s now Southern California, for example, camels appear to have disappeared a little ahead of other megafauna, like mastodons and dire wolves, during a dry period that caused trees in the region to die back. The intense droughts, partly a consequence of a warming and more arid planet, likely tipped the last of North America’s camels into extinction just before humans used fire to transform woodlands into more open chaparral—an incredible amount of ecological stress that made the land inhospitable to the Ice Age giants that had already survived the droughts.

Camels disappeared from the place where their story started, yet their long history on the continent is what allowed these long-necked, extremely adaptable herbivores to find new homes around the planet. With such a storied history, perhaps someday descendants of today’s camels will set off a new evolutionary burst.