Prehistoric Creatures

Ammonites are prehistoric molluscs related to octopuses and squids.

Coelacanths are a group of fish once thought to have become extinct millions of years ago, until living examples were found in the 1930s.

Daeodon was a large, rhino-sized pig-like mammal known as an “entelodont”. It was formerly known as “Dinohyus” or “terrible pig”. Though entelodonts like Daeodon had pig-like physical characteristics, it’s not known if they were directly related to true pigs, and recent studies point to a closer relationship to hippos and whales than to pigs.

This popular sail-backed prehistoric creature is often incorrectly included amongst the dinosaurs, though it actually lived long before the dinosaurs existed, and is more closely related to mammals than dinosaurs.

A flying pterosaur from the Early Jurassic Period (195 million years ago), Dimorphodon is known for its large and unusual skull.

Doedicurus clavicaudatus, pestle tail, was a prehistoric glyptodont with a mace-like clubbed tail. Doedicurus lived during the Pleistocene until the end of the last glacial period, some 11,000 years ago. It lived in North and South America and was the largest known glyptodont. Glyptodonts were heavily armored cingulate xenarthrans related to modern armadillos that evolved during the Miocene in South America. The extinction of the glyptodonts coincided with the arrival of early humans in the Americas and evidence suggests that these humans made use of the animal's armored shells.

Dunkleosteus was a large prehistoric fish that lived over 350 million years ago.

Elasmosaurus was a prehistoric marine reptile with an amazingly long neck.

This prehistoric creature's head was covered in unique horn-like structures. It lived over 260 million years ago!

This giant ground sloth from South America lived in the Pliocene and Pleistocene. It is one of the largest mammals to have ever lived, with a size exceeded only by Mammoths and some giant rhinos. Ground Sloths are xenarthrans, a distinct group of South American mammals that includes the living anteaters, tree sloths, and armadillos and the extinct megafauna, glyptodonts, and pampatheres. It had a close relative, Eremotherium, that migrated to North America during the Great American Interchange when the land bridge connected the continents.

Hyaenodons, despite their similar names, were not related to present-day hyenas. They also weren’t particularly hyena-like in their appearance or behavior, which likely bore a closer resemblance to modern-day wolves. Hyaenodons were widespread apex predators in their time, and the largest of these was Hyaenodon Gigas.

Ichthyosaurus (Ick-thee-oh-sore-us) lived during the Late Triassic and Early Jurassic Periods, around 200 million years ago. It looked like a dolphin, with a sleek body, long snout, and fins. However, it was a reptile that had become completely adapted to aquatic life.

Kaprosuchus was a crocodile relative from the Middle Cretaceous Period (around 100 million years ago) with tusks resembling that of a boar.

A giant seagoing predator, Kronosaurus was named for a titan of Ancient Greek mythology.

Liopleurodon was a predatory prehistoric marine reptile that lived in the Jurassic Period, around 160 million years ago.

This prehistoric mammal lived in South America from 7 million years ago to around 10,000 years ago.

Mastodons are elephant-like creatures, the most well-known of which is the American mastodon. Though similar in appearance to woolly mammoths and elephants, they are found in a different family, the Mammutidae.

Megacerops was a Brontohere, which means “thunder beast”. This family contained the largest land animals during the Eocene epoch. Though they possessed large bony protrusions on their snouts, they were not closely related to the rhinoceros they resembled.

Megalodon was a massive shark that lived millions of years ago that is believed to have grown longer than 50 feet in length!

Mosasaurus was a marine reptile that lived up until 66 million years ago. It could grow to over 40 feet long.

Postosuchus was a large predator that prowled North America at the beginning of the age of the dinosaurs, approximately 210 million years ago. It was not a dinosaur, but a type of reptile called a rauisuchid. Postosuchus was the largest predator in its ecosystem.

Prestosuchus looks like a dinosaur, but it was actually an early ancestor of crocodiles that lived during the Triassic Period, around 240 million years ago. Its remains were discovered in what is now Brazil in South America. It was related to other early crocodile relatives like Postosuchus.

Pteranodon was a winged pterosaur that lived in the Late Cretaceous of North America around the western interior seaway that divided North America. Pterosaurs were not dinosaurs, but they were related to them, as both belonged to a group called archosaurs. Pteranodon was a close relative of the nyctosaurs, one of the two groups of pterosaurs that lasted until extinction at the end of the Mesozoic around 66 million years ago. Pteranodon is often called “pterodactyl” incorrectly. There is no actual pterosaur named “pterodactyl”; the closest is a very small pterosaur known as “Pterodactylus” which is very different from Pteranodon.

One of the largest pterosaurs of all time, this prehistoric flying reptile had a wingspan of nearly 40 feet!

Rhamphorhynchus was a flying reptile called a pterosaur that lived around 150 million years ago during the Late Jurassic Period.

Sarcosuchus (Sar-koh-sook-uss) lived during the Early Cretaceous Period, around 112 million years ago, in what is now South America and Africa. It was a huge relative of crocodiles, and one of the largest croc-like animals to ever live.

Shringasaurus (Shreen-guh-sore-us) was a prehistoric reptile living in the Middle Triassic Period, around 240 million years ago, in what is now India. It had two large distinctive horns on its head, like the ceratopsian dinosaurs that would appear millions of years later.

Often called the “sabre-toothed tiger” or “saber-toothed cat”, Smilodon wasn’t actually a close relation of modern tigers, or today’s cats in general. While in the feline family, it belonged to a now extinct subgroup called Machairodonts.

Tapejara lived in Brazil around 112 million years ago during the Cretaceous Period. Like many other Cretaceous pterosaurs, it had a distinctive head crest.

Tylosaurus was a marine reptile called a mosasaur, thought to be closely related to modern day monitor lizards.

Uintatherium was a large, rhinoceros-like plant-eating mammal that lived during the Eocene epoch roughly 40 million years ago. The most striking feature of these beasts were the six bony knobs on their unusual skulls.

Massive, thick-furred elephant relatives, mammoths once walked the frozen plains of the Pleistocene Epoch, where they were hunted by early humans.

The Woolly Rhinoceros lived from three and a half million years ago up until about 10,000 years ago, and was depicted by early humans in cave paintings. Unlike most rhinos of today, it was covered in shaggy fur to protect it from the harsh cold climate it lived in.