10 Extinct Creatures That Would Destroy Earth Today

Imagine walking through a forest only to realize you're being hunted by a 40-foot snake, or on a dive in the ocean and noticing a great white shark trying to escape a predator so big it makes the great white look like a minnow. These creatures seem to be straight out of a nightmare but, if we may paraphrase, nature is stranger than fiction. Throughout Earth's history, there have been five mass extinction events that have wiped out thousands of species, paving the way for humans to become the dominant species. But within each of these extinctions there were giant creatures that would've given us a run for our money. 

These terrifying animals, if alive today, would wreak absolute havoc and destroy the world as we know it. From apex predators capable of annihilating the food chain as we know it to colossal herbivores that would have devastated ecosystems, these giants could unleash chaos if resurrected, upending the delicate balance of life we see today with the terrifying power of nature and its lost creations. 

Saber-toothed tiger or Saber-toothed cat; whatever you call it, be glad the smilodon (Smilodon fatalis) isn't around any more. Scientists believe smilodon was a fantastic ambush predator able to take down prey as large as Mastodons, so it could easily become an apex predator in today's world. It had a unique skull shape that allowed stronger neck muscles to evolve, which may have helped it hold onto large animals. Its mouth was terrifying, with jaw muscles that could stretch and let it open its mouth up to 90 degrees, showing razor-sharp molars and canine teeth as long as 8 inches each. Plus, its short, powerful legs gave it the ability to run in bursts as fast as 30 mph, easily outpacing top sprinters like Usain Bolt, who peaked at 23.35 mph. Just imagine if it caught up to you next. 

Current fossil records show smilodon may have been a social animal, living and hunting in packs, which only further helped it dominate its territory. Smilodon went extinct only 10,000 years ago, which means it was around long before humans migrated worldwide and may have competed with our ancestors for food. Their exact cause of extinction is a hot topic in paleontology, with some believing climate change led to a decline in prey, while others say the fossil records show no proof of prey decline. Regardless of the cause, we're glad we don't have to compete with them any more. 

The megalodon (Otodus megalodon) is believed to have been the largest fish that ever existed. Weighing as much as 75 tons with a length between 40 to 60 feet, megalodon was estimated to be at least three times bigger and 30 times heavier than the average great white shark. Scientists believe it also may have had a higher average body temperature than great whites, which would've made it faster, able to swim deeper, and have a wider diet, all of which would've decimated our already fragile oceanic ecosystems. 

The megalodon may have been the king of Earth's oceans for up to 20 million years, going extinct around 3.6 million years ago. Scientists believe it may have been warm-blooded, letting it adapt to more tropical waters but at a significant cost. Maintaining that higher body temperature meant it needed massive amounts of food, and its prey resources could have diminished due to climate shifts and changing oceanic currents. Researchers are currently developing new technology to study the tooth fossils we currently have to hopefully give us insight into how current ocean changes may affect sharks now. 

Not all world-destroyers are fearsome carnivores; some herbivores were more than capable of causing modern-day destruction, too. The woolly mammoth (Mammuthus primigenius) is one such example, with its large size and potential for quick bursts of aggression becoming a fearsome combo for humans to confront. Woolly mammoths needed massive amounts of food to nourish their 12-foot-tall, 8-ton bodies, and could have destroyed forests all over today's Northern Hemisphere. While they did live around — and were hunted by – humans, they weren't our competitors. That said, fossil records show male mammoths had periods of extreme aggression that would've made them pretty cranky and quick to use those sharp tusks if they needed to.

Despite being a relatively recent animal to live alongside humans, scientists aren't entirely sure when mammoths went fully extinct or what the cause was. The majority of the population died out around 10,000 years ago, most likely due to a warming climate that made their formerly cool territories too warm for their cold-adapted bodies. However, some may have held on until only 5,600 years ago, eventually succumbing to a lack of water in their former drinking holes and dying of thirst. 

Modern day crocodiles are terrifying beasts. Now, imagine one of those crocodiles growing up to 23 feet with long legs that gave it the ability to run so fast that it would tire out its prey. Enter Quinkana, which was so good at hunting on land that it lived in woodlands and not the water. Today's crocodiles have teeth that are meant for holding onto prey while being dragged under water, whereas Quinkana's teeth were like serrated knives designed to tear its prey to pieces. If it lived today we'd not only have to compete with it for territory — and good luck telling that thing to move — but its massive size and ability to ambush on land would've made it a devastating predator, adding to the already nightmare fuel-inducing Australian wildlife currently living in its former native habitat.

Quinkana mostly lived around modern-day Queensland, though fossils have been found in New Guinea and New South Wales. It lived during the Pleistocene period, dying off around 40,000 years ago, making it one of the last surviving land crocodiles. It may have been around to see the first humans migrate to Australia, but paleontologists don't believe there was enough overlap for one species to affect the other. However, if they did cross one another, both might be in for a fight, as Quinkana hunted mammals, birds, and reptiles. It most likely died out during a time when Australia became incredibly arid, leading to a destruction of its woodland habitats through water evaporation, increased fires, and a collapse of the local food chain.

In Southern China during the Pleistocene period there lived an absolute unit of an ape. Gigantopithecus (Gigantopithecus blacki) is considered to be the largest primate ever, growing as tall as 10 feet and weighing up to a staggering 660 pounds. Though it was an herbivore, the amount of food it would need to consume would decimate modern forests, while giving pandas a reason to check over their shoulder before grabbing a bamboo stalk. But don't take that herbivore status too lightly; as one of the prehistoric creatures that were pure nightmare fuel, Gigantopithecus was so big and strong that it could easily overpower and kill humans who threatened its home. 

In truth, we don't actually know how big Gigantopithecus got because we only have mandible and teeth fossils. But we have so many teeth – almost 2,000 to date – that scientists are able to draw firm conclusions about its lifestyle and appearance. Based on fossil records, paleontologists think Gigantopithecus was most likely a type of orangutan, even though older depictions show it looking closer to a gorilla. The structure of the mandible tells us that it had a powerful jaw, which would've been helpful since it most likely fed on a diet that consisted mostly of bamboo. Wear on the teeth fossils also tell us that Gigantopithecus occasionally ate fruits, but the cavities we've found mean it probably only saved those for the occasional treat. It may have died out anywhere from 215,000 to 100,000 years ago due to climate change destroying its habitat, though it did have some overlap with Homo erectus that lived in the area. 

When you think of giant North American predators, you most likely think of the Tyrannosaurus rex. But let us introduce you to the terrifying Deinosuchus (Deinosuchus riograndensis), among the largest crocodiles on record. Reaching up to 50 feet long and weighing 7.7 tons, Deinosuchus would lie in wait in swamps and use its 6-inch razor sharp teeth to take down its prey. Scientists believe Deinosuchus was so powerful it could easily take down dinosaurs multiple times its size. If it lived today, not only would every single animal near a waterhole most likely be a tasty snack, but the sheer volume of water needed to maintain a population would cover major swaths of the United States.

During the time of its reign, North America was divided in half by a shallow sea called the Cretaceous Seaway, and Deinosuchus (which translates to the fitting "terror crocodile") lived on both sides, hunting on the west between modern-day Montana and northern Mexico. Its East Coast brethren, D. schwimmeri, owned the coastal plains between New Jersey and Mississippi, so if you came to visit the U.S., it's likely you'd run into a Deinosuchus no matter where you went. 

Despite being considered a crocodile, Deinosuchus is actually more closely related to alligators, but the waters get a little muddy classifying reptiles from the late Cretaceous period. Paleontologists aren't sure what caused its extinction, but it seemed to disappear before the asteroid that killed the dinosaurs came. Still, for 9 million years, it reigned as king of the freshwaters and would've been a terrifying site to see. 

In the shallow waters off the coast of the Southeastern United States, a giant whale once laid in wait. But unlike its modern-day distant cousins, this whale was not looking for krill, but rather something much bigger. Basilosaurus, whose name means "King lizard," looks like a combination of snake and crocodile, growing up to 70 feet long with a mouth full of blade-like teeth that sheared through its prey with ease. If it lived today, the volume of food it would need would mean a total collapse of the oceanic food chain.

Basilosaurus lived all over the Atlantic Ocean and what's now known as the Mediterranean Sea during the Eocene Epoch, around 37.8 to 33.9 million years ago. It had a bite force that was pure nightmare fuel, crushing the bones or shells of its food — mostly sharks, whales, sea cows, and turtles — like they were potato chips.  While it was one of the few sea creatures to have legs, they were stubby things and scientists believe its massive weight would've been too much for them to support on land. Most likely, they used the legs to guide themselves during mating. Thankfully, Basilosaurus was the last of its kind, going extinct during an abrupt cooling of Earth's climate, which disrupted ocean currents around 34 million years ago. 

If you think modern-day boa constrictors or anacondas can get big, let us introduce you to Titanoboa (Titanoboa cerrejonensis), the big daddy of snakes. Reaching over 50 feet long and weighing up to 1.25 tons, Titanoboa is not only considered the largest of any snake that ever lived, but also the largest predator of the Paleocene epoch. Despite its astonishing size, Titanoboa was an excellent ambush predator that could hunt on both land and underwater, and its adaptability and diet would destroy its modern-day South American habitat quicker than you might think.

Titanoboa could consume crocodiles whole, crushing its prey with its massive, muscular body the way modern constrictors do. It reigned over what's believed to be the first-ever tropical rain forest for around 2 million years. Scientists suspect it was able to grow into such a giant thanks to its habitat near the equator and the climate of the Paleocene era, which was around 10 degrees Fahrenheit warmer than today. Since it was cold-blooded and needed lots of heat to stay alive, this warm temperature and ample food supply gave it the perfect opportunity to grow and thrive. But could today's warming Earth lead to another era of giant snakes? Scientists aren't sure, but think it's unlikely due to human intervention. Still, we're thankful this snake is a thing of the past, going extinct around 58 million years ago.

Haast's eagle (Aquila moorei) is no ordinary bird of prey. It's the largest eagle that ever lived and was so fearsome that scientists gave it the nickname "The flying tiger," thanks to its predatory ability and incredibly gruesome method of killing its prey. Haast's eagle is also one of the few animals on this list suspected to have hunted humans, dying out only around 600 years ago. If it lived today, there's no limit to the damage it could do, especially as the human population of its native New Zealand has only grown.

Haast's eagle had a wingspan 10 feet wide and thick, muscular legs that held long, razor-sharp talons. It primarily hunted moa, a bird similar to emu, though it also was happy to snack on other flightless birds or potentially even humans. That giant size, muscular body, and tiger-like claws weren't just for show; moa could weigh as much as 440 pounds, so it was going to take a lot of effort to capture and kill its favorite prey. Once it caught its dinner, Haast's eagle would deliver a killing blow with its thick beak and begin eating its prey's insides, similar to modern-day vultures. 

It seems that humans and Haast's were common enemies, as we have tools made from their bones. Despite being an uncomfortably recent apex predator, Haast's eagle couldn't survive the changes to its habitat caused by humans, like deforestation and their own hunting of moa. Once humans killed off the last of the moa species, Haast's eagle couldn't find enough food to survive.  

Quetzalcoatlus was the largest flying animal we know of to ever exist. This pterosaur possibly hunted from the skies of modern-day Texas, stalking its prey and swooping down to pick it up with a long, sharp beak. But if you think you'd be safe under some trees, think again, because Quetzalcoatlus may have used those giant wings as limbs to walk and was capable of arcing its neck 180 degrees, giving it the ability to see all around it. Were it alive today, there are just too many unknowns about its behavior to be sure it could live alongside modern-day animals. However, its impressive predatory capabilities could have the potential to cause an ecosystem collapse, with it being able to devour a majority of the small prey that other predators rely on for survival.

Quetzalcoatlus lived during the Cretaceous period, and paleontologists believe it stood around 12 feet high, weighed up to 550 pounds, and had a wingspan as wide as 36 feet. Scientists aren't entirely sure if it was capable of flight, just due to its sheer size. However, its hollow bones and leg-muscle build could've given it a leap as high as 8 feet, which leads some to think flight was possible. Regardless of the way it hunted, Quetzalcoatlus used its sharp beak to grab its prey and swallow it whole. It most likely went extinct during the K-T boundary, around 65 million years ago.