Top 10 Incredible Prehistoric Monsters That Actually Existed

Eat your heart out, Jaws. The megalodon’s true size is a subject of debate, with estimates ranging up to sixty-seven feet, but no matter the details, this predator was huge. The massive shark’s name means “big tooth,” and it comes by that title honestly. The megalodon had five rows of teeth and roughly seven-foot-wide jaws. Why did it need a mouth big enough to swallow an NBA player whole? Well, its prey included large species such as dolphins and whales. Although the megalodon went extinct millions of years ago, it still captures people’s imaginations to this day and even stars in books and films. Shine bright, you terrifying shark.

Colloquially called saber-toothed tigers, these extraordinary animals were actually not closely related to any modern cats. Smilodon encompassed several species, ranging from 120 to 1,040 pounds in weight. Although they were different sizes, all Smilodon species shared muscular bodies and, of course, very long canine teeth. Their signature dental features measured eleven inches long and were used to take down prey such as bison and camels. While Smilodon teeth likely couldn’t pierce bone, they were definitely handy when fighting other predators such as dire wolves. They went extinct roughly 10,000 years ago, but their legacy lives on in the City of Angels, where the La Brea Tar Pits and Museum has dug up more than 166,000 Smilodon specimens.

Modern bears are intimidating enough, but prehistoric bears were downright terrifying. The Arctodus simus, or giant short-faced bear, was believed to be between eight and twelve feet tall when standing on its hind legs. However, it didn’t let its massive size slow it down. In fact, this bear could run up to forty miles per hour. Most scientists believe Arctodus simus was an opportunistic omnivore similar to today’s brown bear. While it probably consumed vegetation most of the time, the Arctodus simus might have scavenged meat from the prey of other animals such as the aforementioned Smilodon. Although Arctodus simus went extinct about 10,000 years ago, its surviving relative, the spectacled bear, still roams South America.

If you thought flying roaches were scary… Well, you’re right, but this creature was even more terrifying. The Meganeuropsis’ wingspan was more than two feet, making it the largest insect to ever take flight. These enormous creatures ate other insects, but they were also known to grab small amphibians for lunch. Meganeuropsis - along with seventy percent of land-dwelling animals - was wiped out during the largest known mass extinction event on Earth. Its modern descendant the southern hawker is much smaller, but it is still an extraordinary creature and can reach speeds up to thirty miles an hour in the air.

The Dunkleosteus genus encompassed at least ten species, the largest of which measured up to twenty-nine feet long and weighed up to 8,000 pounds. As if these enormous fishes’ huge jaws and weaponlike beak weren’t intimidating enough, their bodies were covered in armor. Scientists believe Dunkleosteus were powerful swimmers even though their armor slowed them down. Despite their lack of speed, Dunkleosteus species were formidable hunters. They primarily fed on other armored creatures and could open their jaws in twenty milliseconds to capture their prey. Many Dunkleosteus specimens have been found with partially digested prey remains, and researchers believe they might have regurgitated bones as opposed to digesting them. Charming!

The Cambrian explosion, which occurred 541 million years ago, brought about several bizarre species, including Opabinia. At only seven or so centimeters in length, this soft-bodied arthropod is by far the smallest creature on this list, but its tiny size packs quite a bit of strangeness. The miniscule Opabinia had five eyes, which took up a large portion of its head. Although size-wise, it was about as different as possible from an elephant, the two share similar body parts. The Opabinia had a long proboscis that was possibly used to pass food into the mouth under its head. While this creature was undoubtedly strange, we also think it’s kind of cute.

Often referred to as “sea scorpions,” these ancient arthropod species are actually believed to have lived in freshwater environments. Like scorpions, Jaekelopterus had large toothy pincers that they used to capture prey such as other arthropods. They were, however, much larger than their modern cousins. Researchers believe the largest species of Jaekelopterus measured more than eight feet long, and that’s before you count their massive claws. Despite their incredible size, they were believed to be relatively lightweight and agile, allowing them to chase prey in the water. Additionally, Jaekelopterus had specialized eyes that helped them see well in low-light conditions so they could easily find and catch their next meal. We’re just glad we’re not on the menu!

These creatures were the royalty of the sky and are believed to have been some of the largest flying animals of all time. Researchers have found that the largest Quetzalcoatlus species could reach wingspans of thirty-six feet, and they stood nearly ten feet tall at the shoulder. Like today’s storks, Quetzalcoatlus had large, sharp beaks, which they likely used to hunt small animals. Modern research suggests that, despite their size, Quetzalcoatlus were powerful flyers and used their legs to help them jump and take to the skies. These incredible creatures went extinct sixty-six million years ago, but scientists continue to study them and make new discoveries.

These animals were basically millipedes in mega nightmare mode. Arthropleura species could reach lengths up to more than eight feet long, making them the largest land invertebrates that we know of. Because of their extraordinary size, these absolute units probably didn’t have any predators. Even if anything did try to eat them, their exoskeletons were pretty sturdy. In fact, molted exoskeletons likely make up all existing Arthropleura fossils. They went extinct 290 million years ago, but even if humans and Arthropleura coexisted, they wouldn’t pose much danger to us. Scientists believe these arthropods were herbivores and mostly snacked on fruits, seeds and spores. Tasty!

Sure, some of today’s snakes, such as the reticulated python, can reach lengths of twenty feet, but these massive ancient creatures dwarf them in comparison. Titanoboa could grow up to forty-two feet long and weigh 2,500 pounds. Like many of today’s large snakes, the Titanoboa lived in tropical rainforests, and the warmth of their climate might have contributed to their gigantic size. Scientists initially believed Titanoboa might have fed on crocodilians and similar species, but more recent research suggests they primarily ate fish. No matter their diet, we’re just glad they went extinct fifty-eight million years ago so we don’t have to worry about running into them in the wild.