The Online Library of Knowledge

LET'S EXPLORE Prehistoric life

When did the Age of Mammals begin?

Mammals scurry among a dinosaur's bones.Mammals scurry among a dinosaur's bones.By the time the dinosaurs became extinct, mammals had long been in existence. They first appeared during the Triassic Period. For millions of years, most were tiny, shrew-like animals. While the dangerous dinosaurs were about, mammals tried to avoid them. They left their burrows only when darkness fell. Then, after the extinction of the dinosaurs, mammals became the dominant land animals. This was the beginning of the Age of Mammals. 

Mammals of North Africa, about 35 million years agoMammals of North Africa, about 35 million years ago

Early mammalsEarly mammals

Early mammals

Most of the mammals of the period following the dinosaurs' extinction did not look like any mammals alive today. They included the strange, knobbly-headed plant-eater, Uintatherium, and the twin-horned Arsinoitherium. Andrewsarchus was an early carnivorous giant, half-hyena, half-tiger.

Andrewsarchus, 4 m (13ft) longAndrewsarchus, 4 m (13ft) longThen, over the next few million years, many kinds of mammal evolved, including the ancestors of mammals we know today. Some were plant-eaters, others meat-eaters. Some, the bats, even took to the skies, while others lived in the water.

Paraceratherium was the largest land mammal of all time. This prehistoric rhinoceros measured 8 m (about 25 ft) from head to tail and stood around 5 m (16 ft) tall at the shoulder.

© 2020 Q-files Ltd. All rights reserved. Switch to Mobile