Guide Note

Mammals are animals that breath air, produce milk, and are warm-blooded and covered in hair. Only monotremes, the most primitive mammals, lay eggs (these include the Platypus and the spiny Echidna). All others either develop their young in the womb (Placental Mammals), or a pouch (Marsupials).

Fast Facts

1. Mammals are the only animals that have flaps around the ears
2. All mammals have a backbone
3. There are over 4000 kinds of mammals
4. The Blue Whale is the largest mammal living today
5. The Kitti’s Hog-Nosed Bat is the smallest

Mammalian Groups

Monotremes are thought to have diverged from other mammals up to 200 million years ago, while Marsupials and Placental Mammals are thought to have split at least 120 million years ago—these figures, however, remain subject to ongoing scientific debate. The vast majority of mammals, ranging from humans (Homo Sapiens) to Narwhals, are Placental, and Marsupials are the second-largest group, with about 334 species.