Mammals

Mammals

Mammals are vertebrates that evolved from therapsid reptiles during the Jurassic Period about 200 million years ago. The first mammals, known as morganucodontids, were nocturnal insect eaters that resembled modern-day shrews. For the better part of 130 million years, mammals remained small and lived in a world dominated by the dinosaurs. But around 65 million years ago, a drastic shift in climate caused the extinction of more than two-thirds of the animal species on the planet, including the dinosaurs. Mammals survived this bout of climate change and in its wake, diversified and colonized the many newly-available habitats. Today, mammals are remarkably varied, with some 5,400 species occupying every continent on the globe.

Mammals display a remarkable array of adaptations that enable them to inhabit a wide range of habitats. Mammals range in size from the minute bumblebee bat which measures a mere three centimeters in length, to the magnificent blue whale, which can measure 33 meters head-to-tail. Some of the better-known mammal groups include carnivores, rodents, elephants, marsupials, rabbits, bats, primates, seals, anteaters, cetaceans, odd-toed ungulates and even-toed ungulates.