Category Archives: Mammals

What Are Mammals?

When the dinosaurs were wiped out, it gave a group of small, warm-blooded animals the chance they needed to thrive. These were the mammals, distinct from other animals largely because they feed their young on milk. There are now around 5,000 species of mammal. They are grouped into different families and orders, including: MARSUPIALS Marsupials… Read More »


Mammals evolved from a group of reptilelike animals called pelycosaurs. The pelycosaurs lived long before even the dinosaurs and for a while were the largest animals on land. They looked more like lizards than mammals, but their link with mammals is clear from a special hole in the skull behind each eye. As in mammals,… Read More »


During the Permian Period, the pelycosaurs (search the article) evolved into more mammal-like animals known as therapsids. Unlike their sprawling, lizardlike ancestors, the therapsids had a more upright build that let them run and breathe more easily, allowing a more active lifestyle. The therapsids were the ancestors of mammals and became increasingly mammal-like over time.… Read More »


The earliest mammals reproduced by laying eggs, but by the Cretaceous Period mammals had evolved new ways of reproducing. The marsupials and their close relatives gave birth to tiny babies that developed outside the mother’s body, often in a pouch. Today, most marsupials are found in Australia, but in the past they were very common… Read More »


Most large extinct animals are known only from fossils. The thylacine, or Tasmanian tiger, is one of the few that was photographed and even filmed before it vanished. This fascinating animal was a marsupial (a pouched mammal) that evolved the shape, appearance, and lifestyle of a wolf. Thylacines once lived throughout New Guinea, Australia, and… Read More »

Flowering Plants

It’s hard to imagine a world without flowering plants, but today’s colorful varieties only began to emerge during the last age of the dinosaurs, the Cretaceous Period. The beginnings The earliest flowering plant yet identified is Archaefructus sinensis or “ancient fruit,” which was small, low growing, and straggly, and not like the colorful plants of… Read More »

Insect-eaters and Relatives

Many early mammals were not carnivores or herbivores but insectivores, surviving on a diet of insects, worms, snails, and other small animals. They had excellent senses of smell and hearing, but often poor vision. They either made burrows in the ground or lived among the trees. Shy and secretive, many were nocturnal, hunting at night… Read More »


Prehistoric bats such as Icaronycteris were not very different from the ones found today. They even hunted in the same manner—flying around in the night skies and swooping over places where plenty of insects gathered, such as among the trees or above lakes. Some scientists suggest that these early bats flew at night to escape… Read More »

Cats and Hyenas

Prehistoric cats were just as ferocious as their modern cousins and sometimes a lot bigger. Like modern cats, they had powerful, muscular bodies and sharp teeth for slashing flesh. Cats and hyenas share a common ancestor, and early species show features of both types of animal. The group includes some of the most efficient killers… Read More »

Ice Age!

Imagine a world in which ice extends farther than the Arctic and Antarctic—a world in which ice sheets cover large chunks of North America, Europe, and Asia. At times, much of the Earth’s surface has been covered by sheets of ice. These periods of Earth’s history are known as its ice ages, with glaciers a… Read More »