When you think of prehistoric beasts, dinosaurs probably come to mind first. But Earth’s ancient past was filled with incredible creatures that lived alongside, before, or after the dinosaurs yet belonged to completely different animal groups.
This article presents general information about prehistoric creatures based on current scientific understanding. Paleontology is an evolving field, and new discoveries may update what we know about these ancient animals.
1. Dimetrodon
Long before dinosaurs walked the Earth, Dimetrodon prowled ancient swamps with its spectacular sail rising from its back. This reptile lived around 295 million years ago during the Permian Period.
Scientists believe the sail helped regulate body temperature, catching sunlight to warm up or releasing heat to cool down. Despite its lizard-like appearance, Dimetrodon was actually more closely related to mammals than to dinosaurs or modern reptiles, making it a synapsid rather than a true reptile.
2. Pterosaur
Soaring through prehistoric skies, pterosaurs were the first vertebrates to achieve powered flight. These winged reptiles shared the Mesozoic Era with dinosaurs but belonged to a separate group entirely.
Their wings stretched from an incredibly long fourth finger to their bodies, covered in leathery membrane. Some species grew as small as sparrows, while giants like Quetzalcoatlus boasted wingspans reaching 10 metres, making them the largest flying animals ever discovered.
3. Ichthyosaur
Picture a dolphin, but make it a reptile from 250 million years ago. Ichthyosaurs evolved a streamlined body shape remarkably similar to modern dolphins through convergent evolution, even though they were completely unrelated.
Their name means fish lizard, and they thrived in Mesozoic seas for over 150 million years. Large eyes helped them hunt in deep, dark waters. Fossil discoveries have preserved pregnant females with babies inside, proving these ocean dwellers gave birth in the water.
4. Plesiosaur
With a body like a barrel, four flippers, and a neck that could stretch incredibly long, plesiosaurs looked unlike anything swimming in today’s oceans. These marine reptiles glided through Mesozoic seas using their flippers like underwater wings.
Some species had necks containing over 70 vertebrae, perfect for snatching fish with surprising speed. Others, called pliosaurs, had shorter necks but massive heads with powerful jaws. The famous Loch Ness Monster legend likely draws inspiration from plesiosaur descriptions.
5. Megalodon
The ultimate ocean predator, Megalodon was a shark so massive it makes today’s great whites look like minnows. Growing up to 18 metres long, this apex hunter ruled the seas from 23 to 3.6 million years ago.
Its teeth, some as large as a human hand, are commonly found as fossils because sharks constantly replace their teeth throughout life. Scientists estimate its bite force exceeded 18 tonnes, powerful enough to crush a car and hunt whales with devastating efficiency.
6. Deinosuchus
Meet the crocodile that could eat dinosaurs for lunch. Deinosuchus, meaning terrible crocodile, lived during the Late Cretaceous and grew up to 10 metres long, roughly twice the size of modern saltwater crocodiles.
Fossil evidence, including dinosaur bones with Deinosuchus bite marks, confirms these massive reptiles preyed on dinosaurs that came too close to the water’s edge. Their powerful jaws and ambush hunting style made rivers and swamps extremely dangerous places for thirsty dinosaurs crossing their territory.
7. Smilodon
Those iconic sabre teeth weren’t just for show. Smilodon, commonly called the sabre-toothed cat, lived during the Ice Age and went extinct only 10,000 years ago, long after dinosaurs disappeared.
Its massive canines could grow over 20 centimetres long, perfect for delivering fatal bites to thick-skinned prey like bison and young mammoths. Despite the name, Smilodon wasn’t closely related to modern cats. These powerful predators were more muscular and stocky than today’s big cats, built for wrestling prey.
8. Mastodon
Shaggy, tusked, and built for cold climates, mastodons roamed North America until about 10,000 years ago. Early humans actually lived alongside these impressive creatures and likely hunted them.
Though they resembled mammoths and modern elephants, mastodons were a distinct species with different teeth adapted for browsing on shrubs and trees rather than grazing grass. Their name means breast tooth, referring to the cone-shaped bumps on their molars. Climate change and human hunting probably contributed to their extinction.
