Megapiranha 

As one of the deadliest river monsters, these extinct animals originated in Argentina. They were estimated to weigh 10 kilograms, and 71 cm in length. This genus of piranha did not hunt in packs, like the Black Piranha, and may have been solitary hunters. when the Andes Mountains rose, they separated the two basins, which scientists think caused mega-piranha to go extinct. Their habitat shrunk when their watery lairs turned into little pockets. There were no longer prey resources available to sustain its body size. Either way, we’re lucky we won’t run into this piranha while swimming (River Monsters). 

Quetzalcoatlus

The Quetzalcoatlus are extinct animals that ruled the skies towards the end of the Dinosaur Age. These pterosaurs were as tall as the giraffe, and the biggest ones were the largest of all flying creatures during that time period. Through evolution of this species, they helped produce some of the largest flying creatures in the world. They’re members of the azhdarchids, which existed between 144 and 66 million years ago. They have pointed skulls, and some even had short crests, located on the back of their heads. Similar to giraffes, they had long necks, but also long legs and short wings, which were all in proportion to their bodies. They’re pretty terrifying, to say the least, and we agree that looking and pictures of them is enough for us. We wouldn’t want to see these roaming around in the streets (Earth Archives). 

Sarcosuchus

The flesh crocodile is one of the most terrifying extinct animals in the world. They existed 133 to 112 million years ago, and were an average of 30 feet tall and weighed about 3.9 short tons. They were in what is now South America and Africa. Their remains were first discovered in the 1950s, when they found teeth, vertebrae, skull, and scutes.  This is certainly not a beast you’d want to accidentally bump into. They’re also known as ‘super croc,’ and while we feared dinosaurs, these animals were also frightening. To kill its prey, it would use its backwards facing teeth to latch onto it, and then drag it into the water to drown it. Its prey might’ve even included dinosaurs, so you could only imagine what it would do to us (Dinopedia). 

Phorusrhacidae

These extinct animals are frightfully known as “terror birds”. They were carnivorous flightless birds, and roamed the lands of South America during the Cenozoic era, which was around 62 to 1.8 million years ago. They were twice the size of an average human, and were up to 10 feet tall. Interestingly, the phorusrhacids were the only known large predators in South America to migrate north, during the Great American Interchange. For millennia, they were one of South America’s leading predators, but went extinct roughly 2.5 million years ago (Science.org). 

Japanese Sea Lion

These now extinct animals roamed the planet up until the 1970’s. They’re a subspecies of the California sea lion, and previously inhabited the Sea of Japan. Mostly, they roamed around the areas of the Japanese Archipelago. It’s one of the saddest extinct animals on this list, as their extinction was aided by hunting during the 1900s. Since they only recently became extinct, it really shows the impact humans have on animals. Luckily, these sea lions were also pretty tame and not necessarily a threat to human safety unless it was a territory issue (Wikipedia). 

Megalodon

These extinct animals roamed the planet up until their extinction 3.6 million years ago. They were the largest fish to ever exist, and grew up to 15 to 18 meters in length. This surpasses the largest recorded great white shark. Their teeth are probably the most terrifying aspect, which reached up to 18 centimeters long. Their name, megalodon, means “large tooth,” because they’re an extinct species of mackerel shark. Let’s just say that these aren’t the sort of animals you’d want to swim into while snorkeling in the ocean. It could easily fit several humans inside of its mouth. They’re also considered the largest marine predators to ever roam the seas (NHM). 

Deinosuchus

These large crocodyliforms lived from 82 million years ago, up until the end-Cretaceous extinction event. In Greek, their name means “terrible crocodile”, and are mostly related to the modern day alligator. Predators that roamed the planet included sharks, and theropods, like the Tyrannosaurs. Mainly, their prey included dinosaurs and sea turtles. These now extinct animals were huge, and were up to 35 feet in length. It’s never a good thing if you accidentally spot a crocodile or alligator, but it’d be even worse if you accidentally stumbled upon one of these. Luckily, they’re extinct, so we don’t have to worry about that anymore. That’s one less thing to be afraid of (Dinopedia). 

Javan Tiger

Unfortunately, the Javan Tiger was hunted to extinction. It existed in the Sundra Islands, in Indonesia, and was one of three tiger populations that lived there. They were larger than the Bali Tiger, and most closely related to the Sumatran Tiger in size. They existed around 11,000 to 12,000 years ago, during the last glacial period. This is another animal species that saw the impact humans could have on an entire species. Things like this are irreversible, and just an unfortunate effect of human greed (Smithsonian Mag). 

Helicoprions

The Helicoprions is one of the most unique and bizarre looking extinct animals in the world. In fact, their jaws are quite beautiful, and almost look like they should be hanging in an art exhibit. These shark-like fish lived in the seas of Asia, Eastern Europe, North America, and Australia 290 million years ago. The chimeras are their closest relatives. The most interesting thing about them is their teeth, which are spiral clusters, also called “tooth whorls,” with a unique spiral pattern that hangs below their jaw. Even though they’re frightening, they’re also quite beautiful (World Atlas). 

Anomalocaris

The now extinct animals, called the Anomalocaris, were, at one point, the world’s top predators. Over half a billion years ago, these animals roamed the planet. It had a bizarre shape and was a meter long, with flaps on its side, a large fan-shaped tail, and spiked arms, which it used to grab onto its prey. Using its arms and jaw, it would bite into its prey with its square mouth. It was alive during the Cambrian period, and are pretty terrifying to look at, to say the least. At least we don’t have to worry about accidentally running into one of these while conducting our normal day-to-day activities (National Geographic). 

Camelops

We love camels. We think they’re some of the cutest animals in the world. But have you ever heard of another species of camel that is now extinct? We’ve seen many types of extinct animals on this list, but this extinct genus of camels roamed the lands of Central and North America during the Late Pliocene Epoch, between 3.6 million to 11,700 years ago. Their interesting shape had long legs and a single bump on its back. In fact, we still think they’re pretty cute, and wouldn’t mind seeing these in real life, as long as it was from a safe distance. It’s great when extinct animals are actually endearing to look at (Wikipedia). 

Eastern Cougar

The eastern cougar is now declared extinct, over 100 years ago. During their existence, these cryptic animals were quite hard to spot. The white-tailed deer was their main prey, and they stalked the lands of North America. The Eastern Cougar succumbed to extinction because their numbers were deemed too low in order to continue breeding (Wikipedia).

Deinotherium

These terrifying mammals were some of the largest non-dinosaur animals to roam the earth. These extinct animals weighed up to five tons, and were short with downward-curving tusks. They were found in Europe and Asia. They appeared during the Middle Miocene and survived until the Early Pleistocene. They’re similar to modern day elephants, but with more flexible necks. Fortunately, they would’ve probably left us humans alone, as their main diet consisted of leaves. It’s assumed they died out when forested areas slowly turned into grasslands, limiting their food supply (Thoughtco). 

Tasmanian Tiger 

Technically, the Greek name for this animal is “dog-headed pouched mammal,” also known as the Thylacine. It has roots with the “marsupial lion,” the saber-toothed predator that used to live in Australia. It existed during the mid-20th century, and the last known living Tasmanian Tiger was captured in 1930 in Australia. Interestingly, though, it could have existed up until the 2000s, unbeknownst to us. Its short ears were about 80 mm, and it had 46 teeth, with a strong and powerful jaw. It also had a wolf-like head and short legs. Like any other tiger in the world, this is the sort of animal you wouldn’t want to accidentally stumble upon during a walk in the forest (Thoughtco). 

Steppe Bison

These extinct animals are a species of bison, previously located in Central Asia, Europe, and Northeastern Asia. They mostly existed in Alaska about 5,400 years ago. They had very large horns, and went extinct at the end of the last glacial period. Their ancestors were a part of the Ice Age, the ​​Bison bonasus. Throughout evolution, the steppe bison gave rise to the two types of bison we see today, and their DNA still lives on in modern day bison, so we still get to see a tiny bit of these extinct animals roaming the earth today (Britannica).

Pyrenean Ibex

The Pyrenean ibex is one of the four subspecies of the Iberian wild goat. During the Holocene and Upper Pleistocene, they were most commonly found in the Cantabrian Mountains and northern Pyrenees. Interestingly enough, they only recently became extinct in 2000, when a falling tree landed on the last one of their species. That’s certainly a way to go, and almost feels like a terrible joke from the Universe. Imagine being the last one of your kind, only to die from a falling tree? (Wikipedia).

Sabre-Toothed Cat

These extinct animals were known for their terrifying, blade-like canine teeth in the upper jaw that protruded from their jaws when closed. If you ever picture the Ice Age, then these animals are probably the ones that come to mind. These meat eaters are ferocious and vicious, and aren’t the type of cat you’d want to come face to face with. They existed from the Eocene through to the Pleistocene Epoch, which was around 56 million to 11,700 years ago. They also belonged to the Nimravidae family, which became extinct around 37 million to 7 million years ago (Britannica). 

Ground Sloth

We love sloths, and think they’re some of the most adorable animals on the planet. What’s even better is the fact that they’ve been around for so long, that some types of their species became extinct. The Ground Sloth lived from the Early Pliocene through the end of the Pleistocene. These now extinct animals previously roamed around the lands of North, Central, and South America. They disappeared around 10,000 years ago, which isn’t so long if you really think about it. These impressive beasts weighed up to 200-pounds, which is about one and a half humans (Britannica). 

Baiji

Freshwater dolphins are some of the cutest extinct animals on this list. It’s unfortunate that they were possibly driven to extinction due to the impact of humans. Sadly, though, this is the first species in the world to have gone extinct from humans. It’s been twenty years since the last dolphin was seen, so scientists believe it’s safe to assume they’re extinct. In Chinese, they’re known as the “Goddess of the Yangtze,” because they were regarded by local fishermen as the goddess of protection. The last number of the Baiji measured was less than ten, and then their slow decline led to their extinction (Sea World). 

Josephoartigasia Monesi

These extinct animals come from South America. The caviomorph rodents roamed the earth from 4 to 2 million years ago, and weighed a frightening 2,200 pounds. They were about five feet tall – that’s about the size of a human! Their weight means they drastically weighed more than any other currently living rodent. They have large front teeth, used for both fighting other rodents for females and defending against predators. Their measured bite force assumes that it is three times as powerful as a tiger’s force today. That’s certainly a rodent you wouldn’t want to mess with. Just look at their size! (AminoApps)

Archelon

We’ve seen large mammals, but what about large turtles? These extinct animals are the largest turtles to have ever existed. They weighed over 4,900 pounds, and measured around 16 feet from head to tail. That’s huge! Through evolution, modern day turtles have hard shells on their bodies, but the Archelon had a leather carapace. They existed around 100 million to 66 million years ago, during the Late Cretaceous epoch (Wikipedia). 

Megalania

Monitor lizards are terrifying, but large monitor lizards that existed during the Pleistocene Epoch were even more frightening. Even though monitor lizards bite, their bites aren’t venomous or poisonous. Modern day monitor lizards only bite when provoked, so if you see one, your safest bet is to stay far away. These extinct animals wandered the earth roughly 2.5 million years ago, and were 7 meters long. This is the same size as a modern day Saltwater Crocodile. During the time of the Megalania, they were the largest lizards of their time (Dinopedia). 

Andrewsarchus 

These now extinct animals existed during the middle Eocene epoch, in what is now known as Inner Mongolia, China. They have a frightening, canine-like appearance. When you first glance at them, you’d think they’re related to wolves or dogs, but they’re more closely related to the hippo! They had hooves on their feet as opposed to claws. They were as tall as horses, and weighed about a ton. A discovery in 1923 found that their skulls were three feet long with huge teeth (Walking With Wikis). 

Pentecopterus

These extinct animals belong to a group of aquatic arthropods during the Middle Ordovician period, which existed roughly 467.3 million years ago. These giant sea scorpions were predators of the prehistoric seas. It’s a genus of eurypterid, and contains only one species that surpasses the other eurypterids by 9 million years. Modern day sea scorpions aren’t dangerous, but can still cause a minor injury if you accidentally come into contact with one. If we existed millions of years ago and accidentally stumbled upon a giant sea scorpion, it might be a different story (Wikipedia). 

Hallucigenia

During the middle of the Cambrian era, about 500 million years ago, the Hallucigenia existed. These now extinct animals were bizarre, and even though they were tiny – only 2 cm long – they were absolutely frightening. They had enormous spines and claw-like appendages, with a strange face that was only recently discovered. 

Interestingly enough, Dr. Martin Smith, from the University of Cambridge, said: “It looks completely surreal. It is like something from another world.” They more closely resembled a caterpillar, because of its strange appendages, which were shown in the fossils, which were used as food-scavenging tentacles. It was believed they walked the earth on stilted legs. These frightening creatures aren’t ones we would’ve wanted to accidentally find outside or near our home! (Earth)

Edestus

These scissor-toothed sharks are now extinct animals that used to use vertical thrashing to kill their prey. New research discovered they had some seriously crazy external teeth, which they used to their advantage. Their jaw was similar to the Helicoprion, but their arc of teeth was on the floor and on the roof of its mouth. They used their highly curved whorls to subdue and eat their prey. These terrifying extinct animals were found around the world, in the United States, Russia, and the United Kingdom (Earth Archives).

Jaekelopterus

These large eurypterids originated in what is now Europe, 417 million years ago. Known as sea scorpions, these aren’t critters you would have wanted to accidentally step on. They were large, measuring up to 3.75 meters long. These extinct animals were also the largest arthropods to ever exist. Their long claws on the front of their body are definitely terrifying to look at (Pre-historic Earth).

Gorgonops

These extinct animals existed around 260-254 million years ago, during the Late Permian period. They grew up to 10 feet, and were some of the most ferocious predators during that time period. The Gorgonops were also some of the largest carnivores to ever exist, and they had up to 12cm long saber-like teeth, used for killing their prey. Their heads were also dog-like, and the largest known of the species was the size of a large bear, with a 45cm long skull (Dinopedia).

Megatherium

The Megatherium, which are now extinct animals, were some of the largest ground sloths to roam the planet. They were half the size of modern day elephants, and had terrifying claws and teeth. Even though they mainly fed on leaves of trees and bushes, their appearance wasn’t any less terrifying. They roamed the lands of South America during the Cenozoic Era, which began 65.5 million years ago. Interestingly enough, their name means “Great Beast from America.” We can agree that they looked like beasts (Britannica). 

Meganeura 

These frightening monsters were actually dragonflies, found in both Britain and America. They existed 300 million years ago, and were referred to as the “Queen of the Carboniferous Skies,” and had an impressive wingspan of up to 65cm. To put it into perspective, a one foot wingspan is about the size of an Eagle. Millions of years ago, we would’ve found these now extinct animals across the globe. You wouldn’t want one of them to spot you, as they would dive down from the sky and snatch you off the ground – dead or alive (Walking With Dinos). 

Phoberomys 

First, let’s picture a small, modern day rodent. Now, let’s picture the largest rodent to have ever lived. That’s Phoberomys, which are currently extinct animals that used to roam around our planet. They wandered the lands of South America during the Late Miocene, which was 11.6 million to 5.3 million years ago, and the Early Pliocene, about 5.3 million to 3.6 million years ago. More specifically, they lived in the Orinoco River delta. They had high-crowned premolars and were herbivores. Despite the fact they ate only plants, it doesn’t make them any less terrifying (Britannica). 

Haast’s Eagle 

Prehistoric eagles were vicious. They were relentless, and ate other birds. If you happened to spot flightless prehistoric birds, then there were certainly other predatory vultures or eagles in the area. In Pleistocene New Zealand, Haast’s Eagles would prey on juvenile, newly hatched moas, like Emeus and Dinornis. The adult Haast Eagles weighed about 30 pounds, which isn’t much of a difference than eagles today, which weigh about 20-25 pounds (Thoughtco). 

Purussaurus

The Purussaurus, or “Purus Lizard,” lived about 10 million years ago, during the Miocene. These extinct animals were some of the largest crocodilians to ever exist, and were roughly 10 meters long. They also weighed 6 tons and were some of the most vicious predators in their environment. They hunted large mammals, in addition to the Megapiranha, which are extinct animals we saw earlier on this list (Additional Creatures).

Glyptodon

The Glyptodon were relatives of the armadillos that lived during the Pleistocene epoch. Surprisingly, these extinct animals were the size of a Volkswagen Beetle, weighing up to 1,850 pounds. It had squat limbs and a round, bony shell. It resembled the modern day turtle, and roamed the lands of North and South America. Their body shell alone was five feet. You wouldn’t want to mess with the Glyptodon, as their tails were equivalent to a lethal club. They devoured almost anything, including plants and insects (Wikipedia).

Megantereon

These extinct animals were discovered in 1824, and were a genus of the saber-toothed cat. They wandered the lands of Africa, Eurasia, and North America. They’re dated to about 4.5 million years. They mostly resemble the modern-day jaguar, with stocky forelimbs and strong neck muscles that could deliver a powerful bite. Some of their prey included horses and young rhinos and elephants. That just goes to show you how powerful these animals were, and are ones we wouldn’t want to run into. If it could devour an elephant, imagine what it could do to a human? (Dinopedia)

Liopleurodon

These large, carnivorous reptiles would’ve devoured us alive. Luckily, these now extinct animals no longer roam the seas, so we don’t have to worry while swimming in the ocean. They became extinct at the beginning of the Cretaceous Period, and were pretty deadly to other animals around them. It wasn’t until 150 million years ago when they went extinct, because a more vicious reptile emerged, the mosasaur, which ended up destroying the Liopleurodon (History of Yesterday).

Cameroceras

These extinct animals are giant orthoconic cephalopods, which inhabited the earth during the Ordovician period. They were first spotted 470 million years ago. They’re most similar to modern day squids, cuttlefish, and octopus. At the opening of a hard cone-like shell was their head, which was soft muscular tissue. They used their long, slithering tentacles to manipulate and capture prey. If we were alive millions of years ago, these are the types of tentacles you wouldn’t want wrapped around your foot in the middle of the ocean. Just look at how massive that animal is! Their toothed tongue would aid in devouring the flesh of their prey. We wouldn’t even have a chance if one of these captured us (Wikipedia)