Animals That Were Scarier Than Dinosaurs

Coming up are some terrifying prehistoric animals that were scarier than dinosaurs!

October 24, 2023・

17 min read

It’s certainly no stretch to claim that life would have been much scarier if the dinosaurs had stuck around. But the Earth used to be populated by creatures that were even bigger and more ferocious! From super-sized serpents to deep sea monsters and bizzaro critters straight from your nightmares, let's explore some prehistoric animals that were even scarier than dinosaurs.

Dunkleosteus

Some of the most terrifying creatures ever to have lived were water dwellers, and Dunkleosteus is certainly no exception. The brutish fish lived during the Late Devonian period, which was around 370-360 million years ago and is often referred to as the “age of fish”.

That was long before the dinosaurs walked the Earth during a time known as the Mesozoic Era between around 245 and 66 million years ago, which scientists have divided into three periods: the Triassic, Jurassic, and Cretaceous. The 26-32 feet long Dunkleosteus was streamlined and shark-like, with an armor-plated head and a face only a mother could love!

Based on its ferocious appearance, you might be surprised to learn that Dunkleosteus actually lacked any proper teeth, but it had two long, bony blades that could snap and crush almost anything! Furthermore, Dunkleosteus was definitely not a fussy eater. It ate fish, sharks, and even its own kind!

Its fearsome fangs grew continuously and rubbed against each other as they did, acting like self-sharpening shears. To give you an idea of just how powerful its jaws were, scientists have speculated that they could generate up to 8000 pounds of bite force per square inch. For perspective, a lion bite generates approximately 650 pounds per square inch!

Dunkleosteus’ fatal flaw was that it was so greedy that it often suffered from indigestion: fossils of the prehistoric beast have often been found alongside regurgitated and semi-digested remains of fish!

Helicoprion

If you thought getting into the water with a Dunkeosteus was a terrifying prospect, then just wait until you learn about the Helicoprion. The ghastly 270 million-year-old, 20-25 foot-long fish is the star of one of the most vexing fossil mysteries to ever confound paleontologists.

It all began with the discovery of strange, petrified whorls of elongated teeth that looked like nightmarish, fossilized fruity roll-ups. Russian geologist Alexander Petrovich Karpinsky coined the name “Helicoprion” in 1899 after determining that the strange fossils were actually part of a shark-like fish.

His best guess was that the unusual feeding apparatus was attached to the nose of the long-dead creature like a permanently rolled-up party horn. But the remains continued to puzzle paleontologists for over a century. Years spent speculating about the true arrangement of the toothy whorl produced a slew of bizarre visions of sharks with whorls of teeth hanging off their snouts, dangling from their lower jaws, dorsal fins, caudal fins, and even embedded deep in their throats!

It wasn’t until 2013 that a study led by Leif Tapanila from Idaho State University correctly proposed that the coiled tooth row totally filled the lower jaw in a buzz-saw-like formation. As the fish aged, new teeth continually formed at the back of the lower jaw, while there were practically no upper teeth to speak of.

So how did Helicoprion catch and consume its prey? Terrifyingly, paleontologists suggest that, as the jaw closed, the toothy whorl rotated the teeth backward in a saw-like motion. As if all that wasn’t scary enough already, the largest Helicoprion specimen ever found had a two-foot wide jaw!

Terror Birds

The simple fact that scientists nicknamed the Phorusrhacidae “terror birds” should tell you everything you need to know about those frightening creatures. After a meteor wiped out fearsome dinos like the T-Rex and the Velociraptor, the terror bird family rose up to become the top land predator in South America, a title they defended for the next 60 million years!

Those prehistoric feathered beasts grew up to 10 feet tall and had T-Rex-like feet and a hooked beak that could sever the spinal cord of a horse with one fatal blow! Their reign of, terror began before what we now know as Central America existed, when South America was still an Island.

While the likes of saber-toothed cats and wolves took over the job of top predators elsewhere, most of the mammals in South America were happy herbivores. That provided the terror birds with a smorgasbord of plant-munching animals to feast on without any competition. Those swift-moving creatures were equipped with a pickaxe-like beak, which they used to strike downwards and fatally crack the skulls of smaller animals.

But that’s not all, their bony heads could act as a giant meat tenderizer, and they would likely have used their enormous, clawed feet to kick the living daylights out of their prey. During their 60 million-year reign, 17 different species in the terror bird family came and went until they finally disappeared altogether about 2.5 million years ago.

Platybelodon

How do you take a regular elephant, and make it utterly terrifying? You replace its trunk with an enormous, fleshy spork, that’s how! The fantastical creature may look like it was dreamed up by an imaginative 7-year-old, but travel back in time between 8 million and 20 million years ago and you’ll see for yourself that the Platybelodon was once as real as they come.

The ancestor of the modern elephant had a strange, jutting jaw that actually consisted of a second pair of widened tusks, which, are just modified incisors. But what was the purpose of that bizarre tool?

After all, animals don’t waste energy developing worthless characteristics. When the Platybelodon was first described in the 1920s, it was thought that their lower incisors were used to shovel, scoop, dig, and dredge soft vegetation in aquatic or swampy environments.

But in 1992, paleontologist David Lambert proposed that they were also used as scythe-like weapons that could slice through thick vegetation. Instead of roaming shorelines, platybelodon wandered around Miocene Asia, Africa, and North America feeding on terrestrial plants, grasping branches with its trunk and cutting them away with those specialized, built-in scythes.

Because those fleshy, spork-shaped appendages don’t fossilize as easily as bone, we’re actually pretty lucky to know much about those bizarre creatures at all. Thankfully, they did us a favor by dying, sometimes in mass, next to or in rivers, which are prime spots for easy fossilization. Although they may not have posed a major threat to humans if they were still around today, it’s safe to say that those animals still have one of the freakiest features in history!

Andrewsarchus

It’s hard to imagine anything with the name Andrew somehow being more terrifying than a dinosaur, but the ferocious creature says otherwise. Although no complete Andrewsarchus skeleton has ever been found, part of a skull from one of those bad boys discovered in Mongolia in 1923 measured nearly three feet long!

Expedition leader Roy Chapman Andrews decided that the animal must have been a carnivore because of its massive teeth, and named it Andrewsarchus Mongoliensis, after himself. To this day, that is the only specimen ever found belonging to that terrifying species, which roamed East Asia some 45-36 million years ago during the Eocene era.

Paleontologists built up an impression of the rest of the animal’s body using knowledge from its skull and its relation to another bear-like prehistoric creature called a Mesonyx. The result is a 16-foot-long, 6-foot-high vision of pure nightmare fuel.

The heavily built, wolf-like animal walked on four short legs and had a long body and tail, with hoofed feet. It had a terrifying snout with large, bone-crushing teeth and could have weighed anywhere between 1,764lb to over 2,200lbs! In case you needed any more reason to quiver in fear, the monumental size makes Andrewsarchus the largest known meat-eating land mammal that ever lived!

Strangely enough, though, those hoofed beasts are actually thought to be more closely related to hippos and whales, both belonging to a larger order of mammals called artiodactyls. Because Andrewsarchus is only known from a skull and a few other bones, whether it was an active predator or merely an oversized scavenger is up for debate.

Titanoboa

60 million years ago during the Palaeocene epoch, in the swampy waters of what is now Colombia, there lurked the biggest snake that has ever lived: the Titanoboa. Clocking in at nearly 50 feet long and weighing a colossal 2,500 pounds, the super-sized serpent was 10 times as heavy as the green anaconda that rules those same stomping grounds today!

Sadly, though, Titanoboa never went toe to toe with the T-Rex. Existing just a few million years after the fall of the dinosaurs, Titanoboa reigned over the immense, swampy jungle where everything was hotter, wetter, and bigger than it is today.

In keeping with the general theme of bigness, Titanoboa was so large that it pretty much defied the laws of physics. Every living creature has evolved under the constraints of gravity. The only reason why ludicrously massive creatures like the 100-foot blue whale are able to exist is because gravity doesn’t affect giants as much in the sea.

Scientists speculate what Titanoboa must have exploited to reach such enormous size. The creature was so outsized that it probably wasn’t able to get around on land very well and must have spent a large part of its time in the water, behaving more like a water-dwelling anaconda despite looking something like a modern-day boa constrictor.

The giant snake was an ambush predator and relied on its incredible strength to squeeze the life out of its prey, eating anything it laid eyes on. Titanoboa lay in wait and hunted mostly large reptiles, gobbling down giant turtles and even crocodiles! Why and even when Titanoboa went extinct remains a mystery, but just imagine the havoc they’d wreak on us puny humans if they didn’t!

Jaekelopterus

Three words: Giant, sea, and scorpion. You probably never thought you’d read those together in a sentence about a real-life animal! You’ll be pleased to learn that the now-extinct group of Eurypterids, also known as sea scorpions, which belonged to the arthropod order, were mostly small creatures about the size of a human hand.

That is, except for the nightmare-inducing Jaekelopterus, which lived around 460 million years ago during the Silurian period. The spiky sea scorpion grew up to 8 feet in length, easily making it the largest arthropod ever known.

Its segmented, paddle-shaped body was similar to that of the bizarre horseshoe crab except, much more giant. Jaekelopterus moved swiftly underwater thanks to its oarlike back legs, which allowed it to swim rapidly after its prey.

Besides its multiple specialized limbs, the marine monster was also equipped with huge spring-loaded claws which it used to snatch up fish as they passed by.

One fossilized spiked claw discovered in 2007 even measured a whopping 18 inches across! There’s no denying that, if the giant sea scorpion existed today, it could have used those grasping claws to grab you in a deadly embrace and crush your skull like an almond.

The reign of the Eurypterids, including the terrifying Jaekelopterus, was eventually brought to a sudden end thanks to the Permian Extinction around 299-252 million years ago, which wiped out more than 96% of all marine life on Earth!

Phoberomys Pattersoni

You may have noticed that many animals in the prehistoric era were basically just souped-up, jumbo-sized versions of some of the animals that still exist today. And Phoberomys Pattersoni is perhaps the most unnerving example of that theme.

Those real-life ratzillas were the biggest rodents to have ever walked the earth, clocking in at around 10 feet long with another 5 feet worth of tail to boot! Remains of those repulsive rodents have been recovered from several sites in Argentina, Brazil, and Venezuela over the years.

Although their closest living relative is the humble guinea pig, they were more similar in appearance to modern-day capybaras, despite being much bigger and heavier. Examinations of the skeletons of those creepy ratzillas suggest they probably weighed around 800kg, which is around the same size as an American Bison!

Phoberomys Pattersoni’s hind limbs were massive compared to its slender front limbs, which suggests it probably rested on its haunches while feeding, using its smaller forelimbs to gather plant material. Much like the capybara, Phobermys had a deep-set jaw and sharp front teeth which were adapted for their gritty herbivorous diet.

Although they were plant eaters, those tremendous rodents would have had foot-long incisors capable of causing some serious damage if you were to cross them! Phobermys towered over wetlands and nearshore swamps until they mysteriously disappeared some 8 million years ago.

Hallucigenia

It’s not unusual for paleologists to have trouble deciphering what an animal looks like especially when it’s been extinct for 400 million years, but the case of hallucigenia was still much harder than most. In fact, scientists studied the thumb-sized worm for more than 50 years before they were able to determine where its head was!

Back in 1977, British paleontologist Simon Conway Morris happened upon a bizarre 0.5-inch-long fossil that had been found in the Burgess Shale in the Canadian Rockies 66 years earlier. It had already been classified as an annelid worm, which includes leeches and earthworms, but Conway Morris didn’t agree.

In his opinion, the wacky organism could actually walk on several pairs of stilt-like spines, while it also had numerous tentacles sticking out of its back. He named the creature hallucigenia because was so nonsensical it resembled something you’d hallucinate during a bad trip!

But in 1991, researchers Lars Ramskold and Hou Xian Guang turned Conway Morris’ idea upside down, literally! What he had identified as “tentacles” were actually the creature's legs, so the model was flipped. The spines, now located on the creature's back, were probably used for defense.

It wasn’t until 2015 that further analysis conducted by Martin Smith from the University of Cambridge using an electron microscope and samples from the Burgess Shale revealed which end was the worm's head, complete with not only a pair of eyes but a big smile of grinning teeth!

Although scientists don’t know exactly what Hallucigenia ate, the ring of teeth around its mouth were probably used to suck water and food into the gut. It may have been tiny, but there’s no denying the floppy hallucination is seriously unnerving!

Anthropleura

Most people feel uneasy around regular-sized creepy crawlies, but millions of years ago those fearful creatures could grow to insane proportions. Case in point: Anthropleura, an 8-and-a-half-foot-long millipede that roamed the earth during the late Carboniferous Period around 359-299 million years ago.

Although it’s likely that Anthropleura was herbivorous and fed on dead plant matter like modern-day millipedes, there’s no denying that it was still pretty darn terrifying. Fossil trackways that have been discovered suggest that those massive millipedes could move at speed, undulating hundreds of huge legs with unnerving rhythm and swerving to avoid trees and other obstacles.

Ahtropleura were the largest land invertebrates of all time, which means it's highly unlikely they had any natural predators. Their segmented bodies were so flexible that they could probably rear up into a defensive posture and look you straight in the eyes if they wanted to!

Those monumental insects went extinct soon after the end of the Carboniferous period, when the moist climate began drying out, dramatically reducing the rainforests that were their natural habitats. But why don’t we have such massive bugs nowadays?

The leading theory is that prehistoric insects got so big because they benefitted from the surplus of oxygen in Earth’s atmosphere. During the period when Anthropleura lived, the rise of vast lowland swamp forests led to atmospheric oxygen levels of around 30%, which is almost 50% higher than current levels! So, next time someone says climate change isn’t real, just introduce them to the super freaky, super-sized millipede.

Mosasaurus

If you’re a fan of the Jurassic World movies, you may already be familiar with the Mosasaurus. But the thing is, the Mosasaurus isn’t technically a dinosaur. Those great marine reptiles are actually closely related to snakes and monitor lizards, but that doesn’t make them any less terrifying.

The gigantic, warm-blooded carnivore swam seas around the globe some 80-66 million years ago. Though no complete specimens have ever been found, paleontologists speculate that Mosasaurus probably reached lengths of 45-50 feet and weighed around 5 and a half tons that’s bigger than the average City Bus and heavier than two adult rhinoceros!

You might have noticed, that the captive Mosasaurus from the Jurassic World movies has two extra rows of terrifying teeth inside its enormous mouth. You might think that is just a classic example of movie makers bending the truth for dramatic effect, but no.

Just like modern-day snakes, Mosasaurus had pterygoid or “fanged” teeth inside their massive maw, which were anchored to bones in the roof of their mouth. Those teeth, which were embedded in the fleshy tissue of their gums, made it much easier to grip and swallow their prey underwater.

Because of their relation to snakes and monitor lizards like the Komodo dragon, it’s even possible that they had huge, forked tongues, but we may never know for sure because soft tissues rarely fossilize. It should come as no surprise that Mosasaurs were wildly successful predators.

Stomach contents have revealed that those aquatic brutes ate ammonites, bony fish, sea turtles, other prehistoric reptiles like Plesiosaurs, and even sea birds! Their fossils have been found on every content on Earth, even Antarctica! They even became the dominant marine predators during the Cretaceous period, until the K-Pg extinction event that ended the dinos and wiped them out too.

Triassic Kraken

For centuries, fishermen have told tales of a terrifying sea monster capable of capsizing a ship and gobbling up its crew: The Kraken. Those humungous beasts have made their way into their fair share of Hollywood movies, but did they ever really exist?

In 1857, Danish naturalist Japetus Steenstrup examined a large, washed-up squid beak measuring about 3 inches across. He concluded that the Kraken was real and that it was a species of giant squid he named Architeuthis Dux or Ruling Squid.

Since then, about 21 species of giant squid have been described, each from different body parts washed up on the shore. Those elusive creatures roam the depths of the ocean, but it’s hard to know exactly how big they get because whole specimens are hardly ever found.

Some estimates suggest that the Colossal Squid, the largest living species, known only from beaks found in sperm whale stomachs, might weigh up to 1,500lb and reach 33 feet in length! It may not be a squid of Kraken-sized proportions, but did such a beast once lurk in prehistoric waters?

Professor Mark McMenamin of Mount Holyoke College in South Hadley, Massachusetts thinks so. According to McMenamin, there could have been whopping 100-foot-long squids in the early Triassic period that preyed on Ichthyosaurs, which were school bus-sized marine reptiles that looked a bit like modern-day dolphins!

McMenamin first presented the idea in 2011 at the annual meeting of the Geological Society of America in Minneapolis. He based his hypothesis on the bizarre discovery of nine fossilized vertebrae from ichthyosaurs in Nevada, arranged in linear patterns that he argues “resembles that pattern of the sucker discs on cephalic tentacles.”

According to McMenamin, a bona fide Kraken killed those marine reptiles and dragged their carcasses back to its lair for a feast, arranging the bones in near geometric patterns. McMenamin referred to the fact that modern-day cephalopods are intelligent creatures and that octopuses have been known to collect bones, shells, and rocks in their dens.

But other paleontologists aren’t so convinced, with some critics pointing to the lack of evidence that cephalopods actually stockpile their prey. Others have even accused McMenamin of simply reading the bones at the Nevada site like prehistoric tea leaves. But in 2013, McMenamin returned to the Nevada site and discovered another fossil: this time, a fragment that he thinks is the tip of a huge beak belonging to a Triassic kraken.

Unfortunately, the unidentified fossil is too fragmentary to prove the size of the cephalopod it may have belonged to. While there’s certainly little evidence of a truly monstrous squid alive today, McMenamin’s theories suggest that there is reason to believe that squid reached stupendous sizes in the distant past.

And when we consider that only 5% of the vast ocean has been explored so far, it’s entirely possible that something much bigger and scarier than the giant squid once lurked beyond human reach.