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- North American horses. European settlers introduced horses when they landed in the New World. But little did they know the thunderous sound of ancient horses' hooves once covered the continent.
- Glyptodon. Glyptodon looked like a supersize version of its distant relative, the armadillo. Like its cousin, Glyptodon protected itself with a shell made of bony plates.
- Mastodons. Mastodons (Mammut) entered North America about 15 million years ago, traveling over the Bering Strait land bridge, long before their relative, the mammoth, according to the Yukon Beringia Interpretive Centre in Canada.
- Mammoths. Mammoths (Mammuthus) traveled to North America about 1.7 million to 1.2 million years ago, according to the San Diego Zoo. Although there are some anatomical differences between mammoths and mastodons, both are members of the proboscidean family.
- Overview
- 1. Giant Short-Faced Bear
- 2. Saber-Toothed Tiger and Scimitar Cat
- 3. Dire Wolf
- 4. Mammoth and Mastodon
- 5. Giant Ground Sloths
- 6. Camelops
- 7. Giant Beaver
- 8. American Zebra
- HISTORY Vault: Journey to 10,000 B.C.
Many of these giant mammals may have been hunted into extinction as prehistoric humans expanded into North America.
Beavers the size of bears. Sloths weighing more than 3,000 pounds. Seven-foot camels roaming the shores of marshy seas. This was the Ice Age world that humans encountered when they first crossed from Asia into North America roughly 14,000 years ago.
“The North America we know today is not a normal, natural landscape,” says Stuart Fiedel, an archeologist who investigates the prehistory of the Americas. “For most of Earth’s history, certainly through the Pleistocene, there were big mammals all over the place. After humans arrive, though, the really big mammals rapidly disappear, except in Africa and parts of Asia.”
When the glaciers receded in the late Pleistocene (also called the Ice Age), North America was home to dozens of thriving species of extra-large mammals known as megafauna. But around 10,000 years ago, nearly all of those giant creatures were wiped out.
What caused the mass extinction of Ice Age megafauna? That’s an open debate. Most archeologists blame over-hunting by paleo-humans, who would have encountered large prey animals unafraid of the hairless, two-legged newcomers.
Ice Age
Illustration of the Giant Short-Faced Bear in North American during Ice Age.
Giant, indeed. The giant short-faced bear (Arctodus simus) was the largest carnivorous mammal to ever roam North America. Standing on its hind legs, an adult giant short-faced bear boasted a vertical reach of more than 14 feet. The most striking difference between modern North American bears and the giant short-faced bear were its long, lean and muscular legs.
“The short-faced bear was huge and had much longer legs than modern bears relative to the body,” says Fiedel, “which has given rise to the idea that it was a ‘cursorial’ predator, meaning that it ran after prey.”
By examining skeletal remains, paleontologists calculate that the short-faced bear could reach speeds topping 40 miles per hour, making it the fastest bear to ever live. Combined with large nasal cavities, it’s likely that the short-faced bear used its powerful sense of smell to detect nearby carcasses, and its speed and size to chase off the competition.
A 3D rendering of a saber-toothed tiger.
The saber-toothed tiger (Smilodon fatalis) is one of the most iconic animals of Ice Age North America. Saber-tooth skeletons pulled from sites like the La Brea tar pits in Los Angeles were armed with upper canines averaging seven inches long and a jaw that could open an astonishing 130 degrees.
Saber-toothed cats aren’t related to modern tigers—or any living felines at all—and their bodies stray significantly from today’s tigers or lions. They were a foot shorter than an adult lion, but almost twice as heavy (over 600 pounds in some cases). Saber-toothed cats had relatively short legs and a bobbed tail, meaning they were built for ambush attacks, not long sprints.
But saber-toothed tigers weren’t the only big-boned feline hunters of the late pleistocene. The scimitar cat (Homotherium serum), with its four-inch canines, roamed all of North America and was built more like a modern African lion with long front legs for pulling down big prey. An adult scimitar cat could easily take down a young mammoth and drag it back to its cave.
An illustration of the dire wolf from the Late Pleistocene of North America. Its skull could reach up to 12 inches in length and its teeth were larger than today’s gray wolves.
The dire wolf gets its sinister-sounding name from its Latin name, Canis dirus, meaning “terrible wolf.” Despite its wolf-like appearance—they were roughly the same height and length as modern wolves—DNA analysis suggests that the dire wolf wasn’t closely related genetically to the gray wolf at all, but was a distant relative of modern jackals.
“Ancient DNA studies have really shaken up pleistocene paleontology,” says Fiedel. “The dire wolf was less of a wolf than a super-sized, ferocious coyote.”
Dire wolves roamed every inch of North America from the frozen Canadian north down through Mexico and thrived in every imaginable ecosystem from boreal forests to grassland plains to tropical wetlands. Like gray wolves, dire wolves hunted in packs of 30 or more and fed on large prey like mammoths, giant sloths and Ice Age horses.
Illustration of a woolly mammoth.
The woolly mammoth (Mammuthus primigenius) is one of the most famous extinct Ice Age megafauna. Standing 12 feet tall at the shoulders and weighing six to eight tons, the woolly mammoth grazed the northern steppes of Ice Age North America using its colossal, 15-foot curved tusks to dig under the snow for food and defend itself against predators.
But fossil evidence shows there were at least four distinct species of massive, elephant-like animals that called North America home in the late pleistocene.
The American mastodon (Mammut americanum) is the most ancient of the North American “elephants.” Its ancestors crossed the Bering Strait from Asia roughly 15 million years ago and evolved into the American mastodon 3.5 million years ago. The mastodon was shorter and stockier than the later mammoths, and the shape of its teeth indicate that mastodons didn’t graze on grass like mammoths, but ripped off leaves and entire tree branches for food.
Mammoths came to North America much later in two waves. Around 1.5 million years ago a mammoth called Mammuthus meridionalis crossed the Bering land bridge and branched into two distinct mammoth species: the relatively hairless Columbian mammoth (Mammuthus columbi) and the Jeffersonian mammoth (Mammuthus jeffersonii). Then, as recently as 500,000 years ago, the woolly mammoth arrived.
Mammoths spread everywhere in Ice Age North America, ranging from Canada down to Honduras. Nearly all mammoths and mastodons were wiped out in the great megafauna extinction 10,000 years ago, but archeologists have dug up remains showing that lone bands of mammoths still roamed arctic islands as recently as 4,500 years ago.
An illustration of the extinct giant ground sloth Megalonyx making his way through an Ice Age Ohio forest.
Today, sloths are molasses-moving tree dwellers roughly the size of a dog. But in Ice Age North America, sloths were an entirely different beast. The giant ground sloths of the late Pleistocene were bear-sized herbivores that stood 12 feet on their hind legs and weighed up to 3,000 pounds.
One giant sloth species, the Jefferson ground sloth (Megalonyx jeffersonii), was named for Thomas Jefferson, who initially believed that sloth fossils were a type of colossal cat that he dubbed the Megalonyx (“giant claw”).
Like modern sloths, these huge ground sloths were probably slow, awkward walkers with some species shuffling on the curled-in ankles of their hind legs. Ground sloths also had elongated claws like modern sloths, which they would have used to strip leaves and dig for roots.
DNA analysis indicates that all extinct North American ground sloths, including the massive Harlan's ground sloth, originated in South America and migrated north along with ancient opossums and armadillos.
“North and South America were separated until around 2 million years ago when the Isthmus of Panama emerged,” says Fiedel. “Most mammals migrated north to south, but sloths came the other way. In some periods, there were giant ground sloths as far north as Alaska.”
The very first camels on the planet evolved in North America around 44 million years ago. Those ancient camels migrated westward over the Bering land bridge around 7 million years ago, later becoming the one-humped (dromedary) and two-humped (Bactrian) camels of North Africa and Asia. Other ancient species of North American camels migrated south and became the llamas and alpacas of South America.
One of the most widespread camel species in Ice Age North America was the camelops (Camelops hesternus) or “yesterday’s camel.” This two-toed, furry camel stood seven feet tall at its shoulders, weighed 1,800 pounds and had no hump at all. The camelops could travel long distances on its long and lean legs, but it’s not clear if they could survive long periods without water like modern camels.
The giant beaver of Ice Age North America was the largest rodent to ever live. It measured up to seven feet long, weighed more than 250 pounds and its two front teeth (incisors) were as long as bananas.
Although similar in appearance to modern beavers—with oversized front teeth and a flat tail—the giant beaver is more closely related to the capybara of South America. The incisors and molars of the giant beaver were rounded and blunt, lacking the power and precision to fell large trees. And their brains were relatively smooth, a sign that they weren’t intelligent enough to construct dams.
It was long believed that horses were first introduced to North America by Spanish settlers in the 16th century, but archeological evidence has rewritten that history. It’s now clear that indigenous horses roamed North America for 55 million years before going extinct along with other Ice Age megafauna roughly 10,000 years ago.
One of the oldest and most widespread ancient horse species in North America was the American zebra (Equus simplicidens), also known as the Hagerman horse. The American zebra is the oldest known member of the genus Equus, which includes all modern horses, both wild and domesticated.
In both appearance and genetics, the American zebra is most closely related to the modern zebra. The American zebra stood around five feet tall at the shoulders, had a stocky build, and faint stripes along its neck and flank.
Around 2 to 3 million years ago, herds of American horses traveled west over the land bridge into Asia, eventually spreading to Africa. Those ancient horses were the distant ancestors of the domesticated horses that the Spanish re-introduced to North America 500 years ago.
Discover the thrilling story of life on Earth in prehistoric times, when early humans were just starting to inhabit North America and huge climate fluctuations caused a mini Ice Age. How did humans survive?
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- Dave Roos
Feb 7, 2019 · An artist’s interpretation of ice age fauna. Image courtesy of Mauricio Antón. At the peak of the last ice age, 20,000 years ago, when most of northern North America was covered by massive glaciers, much of Alaska was ice-free and home to a diverse assortment of large mammals.
Nov 2, 2015 · First, its ice-age megafauna included iconic species like woolly mammoth (Mammuthus primigenius), steppe bison (Bison priscus), and cave lion (Panthera spelaea) . Second, the local extinctions of megafauna on Alaska’s North Slope occurred at a time when archaeological remains are rare, suggesting that people seldom ventured there ( 15 , 16 ).
Nov 6, 2018 · End of the Megafauna Ross D.E. MacPhee and Peter Schouten (illustrator) W.W. Norton & Co., $35. Today’s land animals are a bunch of runts compared with creatures from the not-too-distant past.
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Nov 24, 2023 · At present time, megafauna populations have decreased to low abundances 63 and a large fraction of surviving megafauna are threatened with extinction 64,65,66, casting further uncertainty on the ...
Nov 9, 2020 · Overkill, glacial history, and the extinction of North America’s Ice Age megafauna. David J. Meltzer Authors Info & Affiliations. Edited by Richard G. Klein, Stanford University, Stanford, CA, and approved September 23, 2020 (received for review July 21, 2020) November 9, 2020. 117 ( 46) 28555-28563.
