Image 1
Tasmanian wolf (Thylacinus cynocephalus)
Thought to be extinct nearly sixty-five years, the Tasmanian wolf was neither a species of wolf nor a dog, but the largest carnivorous marsupial in recent times. Its habitat, which once stretched throughout mainland Australia, was reduced to the island of Tasmania by the 19th century. Humans believed that this nocturnal "tiger," so-called for its stripes, preyed upon domestic sheep and poultry (in fact, it preferred birds, rodents, and possums, and other small marsupial mammals) and therefore hunted it extensively, leading to its extinction.

© AMNH/J. Beckett

Image 2

Tasmanian devil skeleton (Sarcophilus harrisii)
The endangered Tasmanian devil, found on the Australian island of Tasmania, only grows to about one foot tall but has the strongest bite-force of any mammal of its size. This species has recently fallen victim to an unusual, infectious cancer, called devil facial tumor disease, transmitted during fights; this contagion has contributed in part to the reduction of the Tasmanian devil population by half in the last decade.

© AMNH/R. Mickens

Image 3

Woolly monkey fossil (Lagothrix lagothrica)
Found only in the tropical forests of South America, woolly monkeys belong to the Atelidae, a group of Central and South American primates whose ancestors are thought to have evolved first in Africa. The fossil record, though sparse, suggests that the ancestor of all New World primates then dispersed from Africa to South America about 40 million years ago, probably floating over the ocean on rafts of vegetation that ripped free in large storms. Once in South America, these tree-dwellers evolved to display amazing diversity and specialized traits, including long, strong arms and prehensile tails that can reach thirty inches in length and have flexible, hairless tips and skin grooves for gripping tree branches in modern wooly monkeys.

© AMNH/R. Mickens

Image 4

Bootherium bombifrons skull fossil
This extinct musk-ox, which lived 780,000–11,000 years ago, was one of at least four such species found in North America during the Pleistocene; only one still lives today. Both male and female musk-oxen have four-inch-thick horns, and the battles between males during mating season can be spectacularly violent in living musk-oxen. Bulls charge at each other from distances of 50 yards (46 meters), leading with the tops, or bosses, of their horns—a pointed "headgear" weapon.

© AMNH/R. Mickens

Image 5
Proboscis monkey (Nasalis gerardis)
Endangered proboscis monkeys live on the coasts and near rivers in Brunei, Malaysia, and Indonesia. The nose of a male can grow up to 7 inches (18 centimeters) and is believed to attract females, making it one of many mammals that show startling differences between sexes, often to attract mates.

© AMNH/D. Finnin

Image 6
Short-beaked echidna (Tachyglossus aculeatus)
When a nursing baby short-beaked echidna begins to grow spines, it leaves its mother’s pouch, but it comes back to nurse at her milk patches for several months. Native to Tasmania and New Guinea, echidnas are monotremes—unlike most other mammals, monotremes never evolved live birth, but instead lay eggs like their amniote ancestors. Monotremes produce milk for their young, but they lack nipples; instead, their milk oozes out of ducts of their mammary glands onto specialized patches of skin.

© AMNH/D. Finnin

Image 7
Batodonoides (Batodonoides vanhouteni)
What’s the smallest mammal that ever lived? The tiny creature named Batodonoides vanhouteni was so small, it could have perched on a pencil. With an estimated body weight of just 1.3 grams—less than a twentieth of an ounce—it weighed only about as much as a dollar bill. It lived approximately 50 million years ago and is related to modern shrews and moles. Batodonoides was named by American Museum of Natural History paleontologist Michael Novacek.

© AMNH/D. Finnin

Image 8
Indricotherium (Indricotherium)
Indricotherium is the largest land mammal ever discovered. A fully grown adult weighed up to 20 tons—the weight of three or four adult African elephants, which are the largest land mammals alive today. Indricotherium lived in the forests of central Asia between about 34 and 23 million years ago. It was a plant-eater and could stretch its long neck to nibble leaves high in the treetops. Indricotherium needed to eat massive amounts of vegetation to survive, and as the central Asian forests gave way to open grassland habitats, this huge mammal species went extinct. Its closest living relative is the rhinoceros.

© AMNH/D. Finnin