7 Ancient Creatures from Prehistoric Times That Weren’t Dinosaurs

While dinosaurs dominate pop culture, it’s important to remember they weren’t the sole rulers of the ancient world. From enormous flying reptiles with wingspans rivaling airplanes to colossal sea predators as large as buses, many remarkable prehistoric animals are often mistakenly grouped with dinosaurs. Here are seven incredible creatures that deserve equal acclaim alongside their dinosaur counterparts.

1. Dimetrodon

Creatures from the Dimetrodon genus have been celebrated in early paleoart and remain iconic prehistoric figures since the 1800s. Despite their scaly, sail-backed appearance and existence 270 million years ago, they are not dinosaurs. These synapsids share a closer evolutionary link to humans and mammals than to dinosaurs like Triceratops or T. rex. Unlike diapsids, which have two skull openings, synapsids possess a single large opening behind their eye sockets, a trait thought to contribute to the strong jaws seen in their mammalian descendants.

2. Pterosaurs

While modern birds are classified as dinosaurs, the ancient scaly beings that soared through the skies millions of years ago were not. Pterosaurs, a unique group of flying reptiles, fall outside the Dinosauria clade. Unlike birds, species such as Pterodactylus and Quetzalcoatlus utilized wing membranes devoid of feathers to achieve flight. These creatures were the earliest vertebrates to master the skies, boasting wingspans of up to 33 feet, making them the largest flying animals ever known.

3. Plesiosaurs

Should a prehistoric creature inhabit Loch Ness, it wouldn’t be a dinosaur. Plesiosaurs, the marine reptiles often linked to the legend of Nessie, are not dinosaurs. These long-necked, flippered animals thrived in oceans until the Cretaceous period's mass extinction. It’s possible they encountered dinosaurs that ventured near coastal areas.

4. Mosasaurs

Mosasaurs, ancient marine reptiles, were formidable predators of the seas. Unlike their long-necked plesiosaur counterparts, mosasaurs sported shorter necks and enormous, powerful jaws designed for seizing prey. Reaching lengths of up to 50 feet, these oceanic giants surpassed even the size of T. rex. Today, their closest relatives include monitor lizards and snakes.

5. Deinosuchus

While modern crocodiles and alligators may resemble ancient creatures, they are not classified as living dinosaurs. These reptiles, along with their prehistoric relatives in the genus Deinosuchus, fall under the class Reptilia. Deinosuchus, though similar in appearance to today’s crocodilians, was a true giant, measuring up to 40 feet in length and weighing around 7 tons. Dominating rivers and swamps 70 million years ago, fossil records suggest they occasionally hunted dinosaurs.

6. Megalodon

The most formidable predator of ancient times wasn’t a dinosaur or even a marine reptile. Carcharodon megalodon, a potential ancestor of today’s great white sharks, reigned supreme in the oceans for 20 million years. Scientists estimate their size, ranging from 43 to 82 feet, based on their massive 7-inch teeth. Like modern sharks, their bodies were made of cartilage, leaving behind only teeth and a few vertebrae as evidence of their existence. Their true size may forever remain a mystery.

7. Glyptodon

Resembling a blend of a tortoise and Ankylosaurus, creatures from the genus Glyptodon were actually early mammals. These animals roamed South America during the Ice Age, joining the ranks of giant sloths and mammoths as part of the dominant mammalian megafauna. Their massive, scaly shells contributed to their impressive 2-ton weight. Unlike the characteristics of Dimetrodon, the traits of Glyptodon are clearly reflected in modern-day mammals such as armadillos.