Animals That Were Scarier Than Dinosaurs - Part 2

Still scared of dinosaurs? Let's explore some prehistoric animals that were a lot scarier than the dinosaurs.

November 2, 2023・

18 min read

Our prehistoric planet was a terrifying place, predominantly to the rampaging reptiles that once ruled here: dinosaurs! Those monstrous creatures dominated the land for some 160 million years! But they weren’t alone. There were other beasts from back then, and a little while after, that could have given even the biggest dinosaurs a run for their money.

From massive monstrosities lurking beneath the waves to huge human-like goliaths that haunted the forests, here are even more animals that were mega scarier than the dinosaurs.

Arctodus: Short Faced Bear

Coming face to face with a 700 lb grizzly bear nowadays is a pretty terrifying scenario. So just imagine what it was like 2.5 million years ago when Arctodus roamed the earth; a bear that was almost 3 times the size of the modern grizzly!

Nicknamed the giant short-faced bear or bulldog bear, estimates have those beasts weighing in at more than 2,000 pounds at their largest. They stood some 5 feet at the shoulder, and over 12 feet tall on their hind legs, towering over early humans, who stood on average at just 4 ft tall!

The bear only died out about 11,000 years ago due to habitat changes during the Ice Age, which means that some early humans actually encountered that beefy bear in the flesh not so long ago. And that’s not even the half of it.

With its long limbs specially evolved to help it chase its prey, Arctodus would have been the fastest running bear ever, reaching a top speed of 40 miles an hour despite its incredible weight! With a good sense of smell and superb eyesight, it was a savage hunter, regularly sinking its 4 ½ inch long canines into giant bison and ground sloths!

Not only that, its large jaws could extend a bite powerful enough to crush bones, all to obtain the juicy marrow within. It’s estimated that Arctodus had a bite force of 2,000 pounds per square inch when chowing down on its prey; for comparison, an average grizzly has a bite force of just 1,160 lbs per square inch.

Megalania

Lizards aren’t always scary, they’re normally small, and skittery, and they’re usually more afraid of you than you are of them! But 2.5 million years ago, that would definitely have been the other way around.

Because in Australia, during the Pleistocene era, the largest terrestrial lizard to have existed was prowling over the sands: The Megalania. It could reach a colossal 23 feet long and weighed up to 4,300 lbs. So, at its biggest, it weighed the same as an average car!

The youngest fossil remains found so far date back to 50,000 years ago, which means that the first Australian settlers might have run into Megalania! From its stocky size, archeologists believe Megalania would have chowed down on large animals and marsupials, but it wasn't picky, being low to the ground, it would have also snacked on ground-nesting birds, eggs, and chicks too.

Hunting was hardly a problem either, with its serrated, blade-like teeth and heavy-set limbs. Though short, the width of its shoulders offered it great stability and even greater speeds, with it being able to sprint up to 10 feet per second. There's even a possibility that Megalania was scarier than it already sounds.

Even though it seems unlikely some closely related species of that lizard have been found to possess an incredibly potent venom inside jaw glands, which, if Megalania had them, would have acted as a nasty anticoagulant. That means that it would have increased the prey's bleeding, decreased its blood pressure, and led to systemic shock.

As Megalania was a member of the Anguimorpha group, also aptly known as the Venom Clade, containing other venomous lizards such as Komodo Dragons, it could also have been violently venomous. And, if so, that would have made it the largest vertebrate of that kind ever. That's right, a huge, fast, flesh-eating, venom-injecting lizard.

Argentavis

Nothing sends chills up your spine like feeling a huge shadow move suddenly across your body. What could it be? A falling tree? A crashing plane? About 6 million years ago, there’s a good chance it would have been a real big bird. Appropriately named Argentavis, that carnivorous creature was native to Argentina and is believed to be the largest bird ever to take to the air.

At 154 pounds, it was as heavy as a human, but with a wingspan a staggering 22 feet long, that thing was only slightly smaller than a light aircraft! In fact, its skull was so big it was longer than the average human forearm. The graceful Argentavis was a glider, much like today's eagles.

6 million years ago, the Miocene climate was much hotter, and so constant rising columns of hot air were able to keep those gigantic birds in flight. It most likely died out due to lowering temperatures, with their gliding abilities sadly affected by the cold.

However, Argentavis was part of a group of predatory birds called "teratorns" or "terratornis" which, to no surprise, translates to ‘monster birds.’ Those deadly creatures could reach speeds of up to 43 miles per hour, scan large swathes of land in little time, and locate their prey from more than 2 miles away.

Doryaspis

With a cute name like Doryaspis, that creature might sound harmless, but it's actually horrific. Unlike our little blue Dory from Finding Nemo, the Doryaspis was a jawless nightmare from the Devonian Period, over 350 million years ago. In that period, fish were typically slow swimmers and had armored bodies, protecting themselves from predators.

Despite that, Doryaspis sported an oddly terrifying elongated, spiked snout just under its mouth, called a rostrum, which it used to root out its crustacean prey. Those spikes were also lined across its fins, spiking and slicing up anything in its path.

What’s worse, at a size of only 1 ft long and around 1 lb in weight, they would have been so small you’d have barely seen them coming, giving them the perfect opportunity to stage a sneak attack, as I’m sure their crustacean prey knew all too well! That period was commonly known as the Age of Fish.

Mesosaurus

There’s something about stories of massive marine monsters that dwell in lakes and ponds which have captivated and terrified us in equal measure for centuries. Tales of creatures with huge teeth, mega maws, and those stupid enough to go chasing after them, never to be seen again; these stories never get old!

You’ve probably heard of the Loch Ness Monster, but we all know that it’s not real as big scary lake monsters don’t exist. However, back in the Early Permian period, around 299 million years ago, they definitely did. And they looked, sickeningly slim, weirdly elongated, with a mouth full of razor-sharp, needle-like teeth. Meet the mighty Mesosaurus.

Despite the word "saurus" in its name, that creature wasn't a dinosaur; it was an early relative of reptiles, one of the very first marine reptiles on the planet! Its rows of terrifyingly sharp teeth in that narrow maw evolved to pierce the scaley skin of its prey, with its long, narrow tail and webbed feet allowing it to quickly shift direction in the water in an instant.

The very thought of that thing launching out of the water to attack ships and sailors is harrowing, but lucky for us, Mesosaurus rarely grew past 3 ft long, and died out around the Permian extinction event, some 250 million years ago!

Megatherium: Giant Sloths

Sloths are cute: fact. There’s no way you can look at the slow-moving, big-eyed, fuzzy little baby in a basket, and not see one of the most adorable creatures on the planet! Well, that is until you see their giant predecessor, The Megatherium.

Native to South America, it was a truly gigantic mammal that lived from the Early Pliocene some 5 million years ago through the end of the Pleistocene era, about 2.5 million years ago. And it was an elephant-sized species. Megatherium Americanum was one of the largest of its kind, weighing up to 8,800 pounds and growing as long as 20 feet from head to tail, and almost 7 ft at the shoulder!

As it was able to stand and walk on its hind legs, it was the largest bipedal mammal of all time and was roughly 800 times the size of modern-day sloths. At some point in time, those creatures diverged in their evolution, producing a smaller, cuter species.

That might be because smaller variants could climb further up trees, and so no longer had to keep competing for food with their much bigger cousins who were stuck on the ground. Eventually, the smaller species lucked out and were somehow spared disease and extinction, unlike Megatherium. It’s a good job they were actually herbivorous, too, because its astronomical size alone could have crushed anything in its way.

Gorgonops

Despite being on the smaller side, the stocky, brutish therapsid, or early mammal, was a predator from the Late Permian period, around 254 million years ago. Having lived 50 million years before the age of dinosaurs, Gorgonops is like the great, great, great grandfather of all terrifying land mammals.

Although it was only 6 feet in length and stood around 2 feet tall at the shoulder, that animal was one of the key predators in southern Africa during that period. Thanks to those large canines, which were some 5 inches long and protruded almost below their jaws, they looked incredibly fierce.

Not only did they make them look scary, but they used them to rip through the tough hides of their prey and thanks to their height, reach up and puncture their windpipes.

Due to its semi-erect gait, it could travel at higher speeds than other animals at the time, meaning its chosen prey rarely ever stood a chance. The creature eventually met its end in the Permian-Triassic extinction event, a disaster that also wiped out 90 percent of animal life.

Thalattoarchon

The Great White Shark is certainly a scary fish, measuring around 20 feet long, they are one of the biggest predators in the ocean. However, with unearthed skeletons, measuring 66 feet, the long-extinct Ichthyosaur was the undisputed king of the seas during the Middle Triassic period, some 240 million years ago.

One of the biggest genus of Ichthyosaur, the Thalattoarchon, had giant, blade-like teeth, measuring 4 inches long. Those were double-edged, and razor-sharp, which is strange. Most fish-eating predators of the time had needle-like, conical teeth that evolved to pierce the slippery skin of octopus and fish scales.

But those teeth were designed to slice straight through the muscle of other marine life. Despite being an Ichthyosaur, Thalattoarchon’s teeth show a much greater resemblance to massive marine reptilian monsters like Mosasaurs, some marine crocodilians, and large Pliosaurs.

That earned it the title of macropredator, which means a relatively large predator, possibly the biggest in its environment at the time! You have to be a pretty big deal to earn that title, especially in the ruling Dinosaur age. And Thalattoarchon rightfully deserved it; weighing in at almost 5 tons, many believe that it was large enough to hunt down other ichthyosaurs, like a fishy Hannibal Lecter.

With skeletal remains showing its skull was twice the size of its prey, and its large jaws of death to boot, Thalattoarchon is believed to be the oldest marine reptile to have been an apex predator.

Megapiranha

Piranhas are dangerous freshwater fish, equipped with a row of serrated teeth and powerful jaws that can take a chunk out of your flesh! But its ancestor, The Megapiranha, was much bigger and much scarier! Where modern piranhas reach around 10 inches in length on average, the 10 million-year-old fish was a terrifying 28 inches long and weighed 22 lbs!

Some remains suggest they may have even been able to grow up to 50 inches long! It could deliver a serious blow to its prey, with its zig zag teeth able to pierce flesh and its powerful jaws able to deliver enough pressure to crush through bone.

It’s thought that Megapiranha fed on hard-shelled animals like turtles and armored catfish, though it could have attacked animals much larger than its own size when part of a school, swarming the animal suddenly!

The largest modern species of that fish, the black piranha, has a top bite force of around 75 pounds per square inch; that is a force that equates to around 30 times its own body weight! By contrast, the Megapiranha holds the heavyweight championship, with a force of up to 1,000 pounds per square inch. That’s about fifty times its body weight!

Liopleurodon

So, we’ve seen quite a few prehistoric predators lurking deep down in the world’s waters, but there’s one that puts all the others to shame: The Liopleurodon. The carnivorous marine reptile from the Middle to Late Jurassic period was a real beast.

One so huge that at its largest, it would have been able to fit an entire human in its mouth with ease. As an apex predator living in the seas of what’s now Europe, it’s believed it could grow up to 30 feet long and could weigh in at some 10 tons at its largest. With a skull roughly a fifth the length of its body, the beastie had a bite that scientists believe was stronger than that of a T-Rex!

The strong paddle-like limbs on either side of its body made it a supreme swimmer. Those specially adapted limbs gave it an unparalleled ability to accelerate quickly in the water, meaning, basically, if you’d ever found yourself face to face with a Liopleurodon in the ocean, there was no swimming away from that monster! Despite that though, Liopleurodon were not fish, they had lungs, not gills.

So they still needed to visit the surface for air, like whales and seals do today. For all that information, scientists aren’t sure exactly what their diet consisted of. Some scientists have pointed to squids, other plesiosaurs, and even ichthyosaurs, but what we do know is that it was the apex predator of the seas some 160 million years ago!

Dimetrodon

Sporting a giant, sail-like protrusion on its back, the Jurassic Park 3 fans among you may be thinking that the guy sounds suspiciously like a Spinosaurus! But the ancient beast, the Dimetrodon, is a primitive Synapsida mammal; dinosaurs, in contrast, were Sauropsida.

Dimetrodon lived from about 286 million to 270 million years ago, with fossils found primarily in North America. The carnivorous beast grew to lengths of over 11 feet and had a large sail of skin on its back, supported by bony spines that experts believe were used for regulating its temperature.

Its teeth were different sizes, making its jaw a jagged cavern of horror! And even worse, as the creature evolved over the years, so did its jaws! They developed even sharper teeth, which kept growing larger, and larger, and larger! Its razor canines were located in the front of its snout, making them ideal for digging their poor prey.

Its back teeth also got involved, able to easily grind up tough muscle and bone. They weren't just scary to look at, but in numbers too. Over twenty types of Dimetrodon have been found since its remains were first discovered in 1878.

Hyaenodon

Existing for a crazy 25 million years in total, Hyaenodon was a long-lasting beast that, from its skull alone, you can tell was not a creature to be messed with. Living in what’s now Eurasia and North America, those vicious, dog-like creatures dominated the lands 40 to 20 million years ago.

In Eurasia especially, they preyed on primitive horses like Brontotheres, early camels, and even early rhinos. Other species went one step further and preyed on other large carnivores, with their tooth puncture marks being found in the remains of Dinictis, also known as false saber tooth cats!

Some species of Hyaenodon were among the largest terrestrial carnivorous mammals of their time; the biggest of them, H. Gigas, weighed in at a staggering 830 lbs and was able to reach more than 10 feet long. Sheer size aside, what made Hyaenodon such a formidable predator was its oversized jaws.

They were so heavy they needed to be supported by extra muscle at the top of their necks. And speaking of necks, those beasts would have likely snapped the ones belonging to their prey in half with a single bite! Then, using the slicing teeth they possessed at the back of their jaws, ground down their meal into smaller chunks of flesh that were easier to swallow!

Gigantopithecus Blacki: The Largest Ape To Ever Exist

We all know that the building-sized ape King Kong is a fictional creature but there was a real massive, prehistoric nightmare that was the closest thing to a real-life King Kong. Known as Gigantopithecus Blacki, the massive, ape colossus lived in the Pleistocene Epoch about 2.6 million years ago.

When stood on two legs, it reached about 10 feet tall, and was a horrifying 1,100 pounds in weight, making it officially the largest hominid ever to stalk the earth. But because of that incredible weight, that thing rarely traveled like us bipedal humans; instead, it supported itself on all fours like most modern apes.

We're lucky that herbivore only ate plants because Gigantopithecus had powerful jaws and huge teeth designed to grind down tough plant matter! While it may look like a massive ancestor of our modern apes, it died out some 300,000 years ago in its native China.

However, some believe that it survived until 100,000 years ago; meaning it could have come across our early human ancestors, homo erectus. It's even believed that Gigantopithecus formed the inspiration for another iconic creature, the Tibetan Yeti, aka Bigfoot.

Sarcosuchus Imperator: Flesh Crocodile Emperor

You may think that the image below shows your average crocodile skeleton. But don’t be fooled. While the creature, who lived some 113 million years ago, has a long snout, a long tail, and a lot of very intimidating teeth, he’s not a modern crocodile. He’s not even a direct ancestor of modern crocodiles, despite his nickname of "super croc".

That is a Sarcosuchus Imperator, native to West Africa, also humbly known as the Flesh Crocodile Emperor. He sits on a different branch of the tree of life to modern crocodiles, a bit like a second cousin once removed!

While modern saltwater crocs are the largest living species of reptile currently, at 9 feet for females and 19 feet for males, estimates have the Flesh Emperor reaching up to an ungodly 40 feet long! That’s more than double the length of a large saltwater croc. And it weighed up to a deadly 9 tons!

With numbers like those, it's the largest crocodilian to have ever lived! It was so big that it’s believed it would have taken some 60 years for them to grow to their full size. And once that happened, they would have been a predator of anything.

From using their huge, backward-facing teeth to pierce the scales of large fish in the water, to lunging out and attacking unsuspecting dinosaurs drinking from their waters! Luckily, there are no descendants of that monster swimming around in our river systems today.

Megalodon

Our next scary animal is the Megalodon, which means, "giant tooth" and that's no exaggeration. The largest fossilized teeth from that beast found so far have measured in at some 7 inches long. It’s estimated that it had a bite force so powerful it was more than 10 times that of a Great White Shark, and 3 times that of the T. Rex, at some 180,000 newtons!

And at more than twice their size, Megalodon makes great Whites look like clownfish! The remains of those beasts have been found in every continent bar Antarctica, and are believed to have roamed the seas from the Miocene, which began 23 million years ago, to the end of the Pliocene, 2 ½ million years ago.

During that time, they were the apex predator, ruling those waters, and chowing down on anything dumb enough to take a swim in them. They preyed upon fish, whales, and seals, with no predators of their own. That allowed the largest, oldest Megalodon remains found to reach up to some 60 feet long, but some scientists believe they could have measured up to 80 feet!

With a body mass of some 70 tons, even most dinosaurs paled in comparison to the sheer size of that sea monster. However, dropping seal levels, destroyed their breeding grounds which were located close to shores, and alongside increased competition with Great Whites for food, that big fish eventually went belly up!

Estemmenosuchus

Estemmenosuchus, which means "crowned crocodile" in Greek, isn’t your typical croc. For a start, it's an omnivorous therapsid, aka a reptilian mammal that eats both meat and plants, that lived during the Middle Permian; around 267 million years ago. They also, unlike crocs, possessed some very distinctive horns!

Those framed their faces and were probably used for display rituals or deliver seriously killer headbutts! Their squat, hulking bodies could reach more than 10 feet long, and their skulls were positively huge; measuring up to 26 inches in length!

Its large, protruding features would certainly have been alarming, if not downright terrifying, to look at; its head alone looks like a cross between a moose, a wolf, and a lizard! Living in the woodlands of what’s now Eastern Europe, it's hard to believe it was a real animal. Coming across it would make you double-take for sure, a 10 ft crocodile-like mammal with antlers.

If you were amazed at these prehistoric animals that were scarier than dinosaurs, you might want to read part 1. You might also be interested in finding out more about the Megalodon and other deadly extinct creatures. Thanks for reading!