A strange wormlike spiny creature appears to have legs and is walking underwater.

10 of the Strangest Extinct Creatures That Have Been Discovered

Nature is full of surprises. Just when you think you've seen it all, another incredible creature appears. According to the National Wildlife Federation, “more than 200 years after biologists began naming and classifying the world´s plants and animals, they still do not know how many species exist. Estimates range from 3 million to 100 million or even more.” Here is a tiny handful of some of the strange creatures that have roamed our world.

Editor's note: updated January 2024 to reflect newly published research on Gigantopithecus blacki.

Thylacine

Thylacine
Image Credit: Shutterstock.

Also known as the Tasmanian Tiger or Tasmanian Wolf, this extinct carnivorous marsupial used to live in every part of Australia, Tasmania, and New Guinea. The thylacine was mainly nocturnal but could also be found during the day. Thylacines mostly preferred to prey on kangaroos and smaller mammals like rodents. The thylacine became extinct on the Australian mainland less than 2000 years ago due to changes in the environment and being hunted by humans. The last known thylacine died in the Hobart Zoo in Tasmania in 1936.

Source: NMA.

Megatherium

Skeleton of Giant ground sloth. Interior view of Natural History Museum in London, UK.
Photo Credit: Lukasz-Pajor/Shutterstock.

Megatherium (M. americanum) is an extinct genus of giant ground sloth found in South America. Scientific records suggest that the beast had enormous claws. Because of the length of its claws, the sloth walked on the sides of its feet instead of the bottom. This giant sloth was able to walk around on its hind legs. When standing on those back legs M. americanum would have stood 12 feet tall!

Based on its mouth and tooth structure, fossil records suggest that the megatherium survived on an exclusively vegetarian diet. According to fossil evidence, it is believed that most megatherium likely started dying out around 12,000 years ago. You can see an entire skeleton cast of a Megatherium on display in the Natural History Museum, in London. 

Source: NHM.

Hallucigenia

Strange worm-bodied creature with multiple stick-like legs.
Photo Credit: Shutterstock

Hallucigenia is a worm-like creature that lived about 500 million years ago. It is a genus of organisms known as lobopodians. These little creatures lived deep underwater. Scientists are unsure of their diet but have found fossil remains near the remains of sponges. They believe that Hallucigenia may have used its clawed legs to hang on and feed on sponges while its spines protected it from predators. The genus Hallucigenia was coined in 1977 when researcher Conway Morris shared his reconstruction of the creature. The name is in reference to its “dreamlike” appearance and also reflects the uncertainty researchers hold over how to classify these organisms.

Source: ROM.

Megalodon

Megalodon
Image Credit: Shutterstock.

Megalodon is an extinct supersized mackerel shark. Like the rest of its body, the megalodon's mouth was huge, too. Its jaws could open wide enough to swallow two adult humans. They fed most likely on whales, large fishes, and probably other sharks. The giant shark has since long gone extinct.

Source: Brittanica.

Woolly Mammoths

Woolly Mammoths
Image Credit: Shutterstock.

The woolly mammoth is an extinct genus of mammoth elephants that were found in the cold tundra of Europe, Asia, and North America about 300,000 years ago. They were probably about the size of African elephants but had much smaller ears, which kept them from losing body heat. Woolly mammoths were herbivores as they relied on plant food, mainly grass and sedges. Woolly mammoths were largely extinct about 10,000 years ago, due to reduced habitat from a warming climate along with humans hunting them. 

Source: Brittanica.

Smilodon

Smilodon
Image Credit: Shutterstock.

Also known as the saber-toothed tiger, Smilodon lived on American soil about 100,000 years ago. Smilodon is the second most common fossil mammal found in California's La Brea tar pits. Through these fossils, we have extensive knowledge of how these animals lived. We know that the Smilodon were carnivores. Their long canine teeth were used for stabbing vulnerable prey, though they were not strong enough to break through bones. Smilodon was incredibly muscular. Fossil records show they were about a foot shorter than modern-day lions but almost twice as heavy! Scientists believe that the muscular beast became extinct about 10,000 years ago.

Source: UCMP Berkley.

Quetzalcoatlus

Quetzalcoatlus
Image Credit: Shutterstock.

These were the largest known flying animals of all time. Quetzalcoatlus dominated the skies over what is now Texas, living in wetlands there over 67 million years ago. They were the size of giraffes, making them the largest flying creatures ever to live. Their 11-meter (just over 36 feet) long wing span means they would have needed to jump 2.5 meters into the air and flap powerfully to take flight. Researchers believe the animals probably hunted like a large heron, plucking fish, and other aquatic prey out of the water and gulping them down whole. 

Source: NHM.

Gigantopithecus blacki

And artist impression of a group of G. blacki in a forest in southern China.
Image Credit: Garcia/Joannes-Boyau (Southern Cross University)

Gigantopithecus blacki was a genus of apes that went extinct 295,000 to 215,000 years ago in southern China. Researchers recently solved the mystery of why G. blacki disappeared.

Surviving on bamboo and fruit, they were the largest apes ever to exist. Evidence shows that G. blacki would have been 3 meters (nearly 10 feet) tall standing upright. This means they needed a significant amount of calories to survive, making size a fatal handicap in a changing climate. 

Titanboa

A gigantic prehistoric snake underwater with little fish swimming by.
Image Credit: Shutterstock

The prehistoric Titanboa was a monster of a snake – over 40 feet long. When paleontologists discovered in the early 2000s, it was so large that it didn't at first occur to them that the bones came from a snake. In an interview with Guy Gugliotta of Smithsonian Magazine, paleontologist Jonathan Bloch said “My only excuse for not recognizing them is that I’ve picked up snake vertebrae before. And I said, ‘These can’t be snake vertebrae.’ It’s like somebody handed me a mouse skull the size of a rhinoceros and told me ‘That’s a mouse.’ It’s just not possible.”.

It was named and described in 2009 as Titanoboa Cerrejonesis. Current research records suggest that Titanoboa probably spent much of its time in water and were piscivorous, meaning that they ate fish and other mammals available for consumption within their habitat.

Chalicotherium

Watercolor rendering of prehistoric huge beast called Chalicotherium
Image Credit: Shutterstock

Chalicotherium is a genus of extinct perissodactyls – the same order that includes the horse and the rhinoceros. Fossil remains of the genus are commonly found in Asia, Europe, and Africa. Unlike the horse, the Chalicotherium had claws instead of hooves. It walked on its claws and likely used them to strip vegetation off of tall trees. This giant herbivore lost its front teeth in adulthood, suggesting it only ate fruits and leaves.

Source: ThoughtCo.

10 Unexpected Facts About the Fluffy Red Panda

Red Panda, Firefox or Lesser Panda relaxing in a tree.
Photo Credit: Depositphotos

Red pandas are not actually related to giant pandas. This ancient carnivorous species is more closely related to skunks, raccoons, and weasels.

18 Interesting Facts About Meerkats

Meerkat peering over a branch.
Photo Credit: Depositphotos

Meerkats, with their tight-knit social structures and quirky habits are definitely interesting. For one thing – they like to eat scorpions!

Author: Chisom Umeh

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