Buzz
In today's world, humans reign as the top predators. However, our reign has only lasted a short time, with the first known human, Homo habilis, emerging approximately 2.3 million years ago.
While we rule over today's animals, many of these creatures had much larger and more menacing relatives in the past. These ancient ancestors are so intimidating, they could have been ripped straight from our worst nightmares. What’s even more chilling is that if humanity were to disappear—or simply lose its supremacy—these terrifying beings, or something similar, could potentially return to life.
10. Megatherium
Today, sloths are slow-moving, tree-dwelling creatures found in the Amazon, posing no threat. However, their prehistoric ancestors were nothing like that. In the Pliocene era, Megatherium, a colossal ground sloth, roamed South America. This giant weighed as much as four tons and measured up to twenty feet (6 meters) from head to tail.
Though it mostly moved on four legs, fossilized footprints suggest it could also walk upright to reach the highest branches. Megatherium was as large as a modern elephant, but even that wasn’t enough to make it the largest animal in its environment!
Researchers believe that Megatherium was a scavenger, often stealing carcasses from other carnivores. It was also among the final Ice Age giants to vanish. Fossil evidence shows that these creatures lived well into the Holocene, the era when humans began to emerge. This points to humanity as the likely cause of Megatherium's extinction.
9. Gigantopithecus
When we imagine a giant ape, most of us picture the fictional King Kong—but gigantic apes actually existed in the distant past. Gigantopithecus was an ape that lived from about nine million to a hundred thousand years ago, overlapping with the existence of several hominid species.
Fossil evidence shows that Gigantopithecus was the largest ape to ever walk the Earth, standing nearly ten feet (3 meters) tall and weighing around twelve hundred pounds (540 kilograms). While the exact cause of its extinction remains unknown, some cryptozoologists believe that reports of Bigfoot and Yeti might actually stem from sightings of this long-lost species.
8. Armored Fish
Dunkleosteus, the largest of the ancient fish known as Placodermi, had a head and thorax encased in articulated armor. Rather than traditional teeth, it sported two pairs of sharp bony plates, forming a beak-like structure.
Dunkleosteus likely preyed on other placoderms that were equipped with similar bony armor for protection. Its powerful jaws were capable of breaking through the toughest of armored creatures. One of the largest specimens discovered measured a staggering thirty-three feet (10 meters) long and weighed around four tons—definitely not a fish you'd want to hook on a line!
This ancient fish wasn’t picky about its meals; it fed on fish, sharks, and even members of its own species. However, it appears Dunkleosteus suffered from indigestion, as its fossils are often found with partially digested fish remains. Researchers from the University of Chicago determined that Dunkleosteus had the second most powerful bite of any fish. These formidable armored fish became extinct during the shift from the Devonian to the Carboniferous periods.
7. Terror Bird
While most flightless birds today—like ostriches and penguins—pose no threat to humans, there once existed a flightless bird that struck fear into the earth itself.
Phorusrhacidae, commonly referred to as “terror birds,” were a group of carnivorous, flightless birds that dominated South America’s predator scene between sixty-two million and two million years ago. Ranging from three to ten feet (1-3 meters) tall, these birds primarily preyed on small mammals... and, interestingly, horses. Their enormous beaks were deadly, capable of killing in two ways: by lifting smaller prey and slamming it into the ground, or by delivering precise strikes to vital areas.
While archaeologists have not fully determined the cause of their extinction, the last fossil evidence of these birds appears around the same time as the emergence of early humans.
6. Haast’s Eagle
Birds of prey have always captivated human imagination; fortunately, we are far larger than even the biggest eagle. However, there were once raptors large enough to consider humans as potential prey.
Haast’s eagle once inhabited the South Island of New Zealand and was the largest eagle ever known to exist. Weighing up to thirty-six pounds (16.5 kg) and boasting a wingspan of ten feet (3 meters), this apex predator targeted the moa, enormous, flightless birds that weighed about three hundred pounds and had no defense against the eagle’s powerful strikes and incredible speed, which reached up to fifty miles (80 km) per hour.
Early settlers and native Maori legends claimed that these mighty eagles could carry off and consume small children. However, human settlers in New Zealand heavily hunted large flightless birds, including the moa species, ultimately driving them to extinction. With the loss of its primary food source, Haast’s eagle disappeared around fourteen hundred years ago.
5. Giant Ripper Lizard
Today, the Komodo dragon reigns as the largest and most fearsome lizard on Earth—but it would have paled in comparison to its ancient relative. The megalania, also known as the “Giant Ripper Lizard,” was an enormous monitor lizard. While exact measurements are debated, recent studies suggest the megalania grew to about twenty-three feet (7 meters) in length and weighed around thirteen to fourteen hundred pounds (600-620 kg), making it the largest terrestrial lizard ever to have lived.
The megalania’s diet mainly consisted of marsupials, such as giant kangaroos and wombats. This massive lizard was part of the clade Toxicofera, equipped with toxin-secreting glands in its mouth, making it the largest venomous vertebrate known to have ever existed. While it's hard to imagine such a giant lizard roaming the Australian Outback today, early Aboriginal settlers may have encountered living megalanias. The species most likely became extinct when early human settlers hunted down the megalania’s food sources.
4. Short-faced Bear
Bears rank among the largest mammals on Earth, with the polar bear being the largest land carnivore. The short-faced bear, also known as Arctodus, lived in North America during the Pleistocene. Weighing around one ton (900 kg), it could reach a height of fifteen feet (4.6 meters) when standing on its hind legs, making it the largest mammalian predator to have ever existed.
Despite its massive size as a carnivore, archaeological evidence reveals that the short-faced bear was likely a scavenger. Being a scavenger was advantageous, especially when competing with saber-tooth cats and wolves for meals. Like many other large creatures of the Pleistocene, the short-faced bear’s food sources dwindled with the arrival of humans.
3. Megalodon
Before the release of the movie Jaws in 1975, humans’ fears of animals were mainly focused on snakes and spiders. That all changed when the film introduced the fictional, terrifying great white shark as its antagonist, scaring many away from the ocean. Today, the largest great white sharks measure around twenty feet (6m) and weigh up to five thousand pounds (2,275kg). But there once existed a shark that was double the size of the largest modern great white sharks.
Megalodon—meaning “big tooth”—was a massive shark that roamed the oceans between twenty-eight and 1.5 million years ago. Everything about the megalodon was enormous: its teeth measured 7.1 inches (18cm), and fossil evidence suggests this colossal shark reached lengths of 52-67 feet (16-20m). While today’s great white sharks primarily target seals, the megalodon’s preferred prey were whales. Scientists believe it became extinct due to a combination of oceanic cooling, sea level drops, and a decline in food sources. If the megalodon still existed, it’s likely that humans would be a landlocked species. However, the vast ocean still holds mysteries, and there could be a giant great white shark lurking in the depths—meaning the return of something like the megalodon is always a possibility.
2. Titanoboa
Few creatures evoke as much fear as snakes. The largest snake alive today is the Reticulated Python, typically growing up to twenty-three feet (7m) in length.
In 2009, archeologists made an astonishing discovery in Colombia; by comparing the shapes and sizes of fossilized vertebrae with those of modern snakes, they estimated that the ancient titanoboa grew to a maximum length of forty to fifty feet (12-15m) and weighed as much as 2,500 pounds, making it the largest snake ever to have slithered across the Earth. Since it’s a relatively recent discovery, much about the titanoboa remains unknown, but one thing is certain—a fifty-foot snake would terrify anyone, phobias aside.
1. Deinosuchus
Modern-day crocodiles are living remnants of the dinosaurs, but there was a time when these ancient reptiles hunted and feasted on their prehistoric cousins. Deinosuchus, an extinct species related to alligators and crocodiles, roamed the Earth during the Cretaceous Period. Its name, 'Deinosuchus,' comes from the Greek for 'terrible crocodile.'
This ancient crocodile dwarfed anything alive today, reaching lengths of up to thirty-nine feet (12m) and weighing nearly ten tons. Despite its size, its general appearance resembled that of modern-day relatives, complete with large, crushing teeth and a body protected by armored bone plates.
Deinosuchus primarily preyed on large dinosaurs—quite a remarkable claim for any predator—and also fed on sea turtles, fish, and other unfortunate creatures. Evidence of its terrifying power is found in the fossilized remains of an Albertosaurus, whose bones bore tooth marks from both Deinosuchus and the Tyrannosaurus Rex, suggesting these two fearsome predators may have clashed in massive, prehistoric battles.
