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Extreme Mammals

This exhibit closed on September 12, 2010.

Extreme Mammals: the Biggest, Smallest, and Most Amazing Mammals of All Time showcases some of our most intriguing relatives, from the speedy to the sloth-like, the towering to the tiny, even the venomous and the armor-clad.


About the Exhibition

With Extreme Mammals: The Biggest, Smallest, and Most Amazing Mammals of All Time, the Academy explores the surprising and often extraordinary world of extinct and living mammals.

Featuring spectacular fossils and other specimens from the Museum’s collections, vivid reconstructions, and live animals, the exhibition examines the ancestry and evolution of numerous species, ranging from huge to tiny, from speedy to sloth-like, and displays animals with oversized claws, fangs, snouts, and horns.

Through the use of dynamic media displays, animated computer interactives, hands-on activities, touchable fossils, casts, taxidermy specimens, and a live tree shrew, the exhibition will highlight distinctive mammalian qualities and illuminate the shared ancestry that unites these diverse creatures.

The exhibition is divided into nine sections – Introduction, What is a Mammal?, What is Extreme?, Head to Tail, Reproduction, Mammals in Motion, Extreme Climates, Extreme Isolation, and Extreme Extinction – and offers extensive detail on the evolutionary history and great family tree of mammals.

Buy tickets

Please note: Passes are not required for the Extreme Mammals special exhibit; the exhibit is available on a walk-up basis. Photography and food and beverage are not permitted in the exhibit.

Extreme Mammals is organized by the American Museum of Natural History in New York, in collaboration with the California Academy of Sciences, San Francisco; Canadian Museum of Nature, Ottawa Canada; and Cleveland Museum of Natural History.

Photo: © AMNH/D. Finnin


Extreme Life

Mammals aren’t the only animals with extreme adaptations. For the duration of the Extreme Mammals exhibit, special signage will call attention to extreme features and behaviors of other specimens and live animals throughout the Academy. For example, in the museum’s Rainforests of the World exhibit, the green anaconda is called out as the heaviest snake species, and, in the Northern California Coast exhibit, the giant Pacific octopus is identified as the smartest invertebrate.


Darwinius masillae

See an exact cast of Darwinius masillae (nicknamed Ida), one of the most complete and beautifully preserved primate fossils ever found. You can see almost every bone in the skeleton, outlines of skin and fur, as well as preserved stomach contents from the young animal’s last meal of fruits and leaves.

Fun Facts:

  • Extinct: Lived about 47 million years ago in what is now Germany
  • Length: About 2 feet (58 centimeters), including tail
  • Fingers and toes have nails instead of claws
  • Opposable big toes, like nearly all primates

Photo: © AMNH



The smallest mammal that ever lived could be sitting right on your shoulder and you would hardly know it. Batodonoides vanhouteni, which lived about 50 million years ago in what is now Wyoming, was so small that it could climb up a pencil – and it weighed as little as a dollar bill. Several slightly larger species of these mini-mammals lived between 55 and 42 million years ago, but they are now all extinct.

Fun Facts:

  • The closest living relatives to Batodonoides are modern day shrews and moles.
  • The smallest mammal alive today is the bumblebee bat, which is only slightly larger than Batodonoides.
  • While Batodonoides is the smallest mammal ever, the largest animal – mammal or otherwise – is the blue whale, with a heart the size of a small car.

Photo: © AMNH/D. Finnin


The Platypus

The platypus is a monotreme – a group where the females produce offspring by laying eggs. Giving birth this way is extremely unusual among living mammals – but normal for most other animals. Almost every other vertebrate, including most reptiles, amphibians, fish and birds, reproduces by laying eggs.

Fun Facts:

  • A female platypus usually lays only two eggs at a time, rarely leaving her stream-side den while nursing her young. When she does leave, she plugs the den opening with dirt.
  • The platypus is one of just a handful of mammals that lay eggs. Another monotreme? Echidnas – commonly referred to as spiny anteaters.
  • A platypus’s bill can sense tiny electric currents produced by the bodies of small animals, helping it hunt in muddy water.

Photo: © AMNH/R. Mickens



As many mammals that developed horns, antlers, tusks or ossicones – from deer and sheep to cattle and goats – no early mammals had horns on their heads. Despite the original lack of headgear, some mammals, like the male moose, evolved antlers as wide as a car over millions of years. Others, like Embolotherium andrewsi, developed horns as support systems for their giant noses (and to head-butt rivals).

Why do we now see these extreme examples of headgear when mammals once roamed the earth with plain-old heads, bones and teeth? Defense, recognition and mating – three common reasons threaded throughout evolution. Nearly all mammals with headgear are prey animals and sometimes use their headgear as defense against would-be attackers.

Photo: © AMNH



Mammals have large brains for their body size – larger than most members of other vertebrate groups. Just as mammals come in all sizes, so do their brains. But it’s the size of the brain relative to the size of an animal’s body that really matters.

Humans claim the largest brain relative to body size at more than seven times the predicted size ratio. But the same relationship does not hold true for all individual parts of our brain. Our olfactory bulb – the area of the brain that processes smells – is smallest in relative size when compared to the opossum, the wolf and the platypus. The winner? The opossum.

Photo: © AMNH



Giving birth to live, well-developed offspring is ‘normal” for most mammals, but more than 300 species of living extreme mammals do things differently.

The average female human is pregnant for about 280 days and its baby is completely helpless at birth. Human babies actually remain dependent on their parents longer than any other species – mainly because our unusually large brains take years to fully develop.

A female giraffe is pregnant for about 457 days – some six months longer than a human. And when the giraffe finally does give birth, the young are so fully developed that they can walk within hours. This adaptation is common among large, hoofed plant eaters that live in open spaces and must be able to flee from predators.

A small handful of mammals, the monotremes (such as the platypus), lay eggs. This is unusual for mammals but normal for most other vertebrates.

Marsupials give birth to tiny, hairless, and immature young who further develop in their mothers’ pouch. There they continue to grow, getting nourishment by drinking milk.

Photo: © AMNH


Extreme Extinction

Ninety-nine percent of all mammals and other species that have ever lived are extinct.

Extinction is always happening. It’s a natural part of the history of life.

But every once in a long while, a great number of species disappear rapidly – something scientists call a mass extinction.

Five mass extinctions are known to have occurred in Earth’s history, but when are we due for the next one? It actually might be occurring right now.

Starting about 100,000 years ago, large mammals and other species began to disappear more swiftly than normal as humans spread from Africa to other continents. Then, the extinction rate sped up beginning about 12,000 years ago and continues to accelerate today. Many scientists think that these extinctions may be leading to another mass extinction event – called the Sixth Extinction.

Along with ground sloths, saber-tooth cats and dire wolves, many other large, astonishing mammals roamed North America until about 12,000 years ago. There were beavers the size of grizzly bears and short-faced bears that stood 11 feet (3.4 meters) high. Woolly mammoths and mastodons strode the Earth – even camels and zebras were common.

But they all died out at the end of the last Ice Age. What caused all those massive North American mammals to become extinct?

Power plant


Humans first arrived in North America about 15,000 to 20,000 years ago. Not too long after, many of these large mammal species went extinct. This pattern recurs on many other continents and islands: as humans arrive, other mammals disappear.

But did humans cause these extinctions? Besides overhunting by humans, scientists have proposed several competing hypotheses such as climate change, killer plagues, and a comet impact or atmospheric explosion. It is likely that a combination of factors – not just humans – are responsible for the extinction of these large mammals in North America about 12,000 years ago.

Photos: © AMNH


Media Sponsors

The Academy wishes to thank the following media sponsors of the Extreme Mammals exhibit:

KGO TV 7, Univision 14, Telefutura 66



Extreme Mammals was located in the Forum on Level 2.

Academy Floor Plan

Extreme Mammals Quiz


Batodonoides was the smallest mammal that ever lived. Can you guess how much it weighed?

  • the weight of a penny (2.5 grams)
  • the weight of a quarter (5.7 grams)
  • the weight of a dollar bill (1.3 grams)



This tiny creature was so small it could have perched on a pencil!


Batodonoides weighed about as much as a dollar bill (1.3 grams).


Koalas are most closely related to which of the following:

  • opossums
  • bears
  • rabbits



Both koalas and opossums are marsupial mammals and have a pouch in which females carry their young through early infancy.


Koalas are most closely related to opossums.


This one-foot-tall creature has the strongest bite-force of any mammal of its size. What is it?

  • red panda
  • raccoon
  • Tasmanian devil



The Tasmanian devil uses its powerful jaws to deliver a fearsome bite.


The correct answer is Tasmanian devil.


Unlike most other mammals, the short-beaked echidna lays eggs. It is native to Tasmania and what other location?

  • New Zealand
  • New Guinea
  • Fiji



The short-beaked echidna is native to Tasmania and New Guinea.


The short-beaked echidna is native to Tasmania and New Guinea.


The platypus belongs to what group of egg-laying mammals?

  • marsupials
  • monotremes
  • placentals



Unlike most other mammals, monotremes never evolved live birth, but instead lay eggs like their amniote ancestors.


The correct answer is monotremes.


This diorama shows what type of habitat from 50 million years ago?

  • Arctic island
  • South American rainforest
  • Southeast Asian island



Instead of the glaciers and frozen tundra plains found in the Arctic today, this area contained warm, humid swamps, and forests of giant trees 50 million years ago.


The correct answer is Arctic island.


Indricotherium is the largest land mammal ever discovered - a fully grown adult weighed up to 20 tons. Which of the following is its closest living relative?

  • rhinoceros
  • elephant
  • hippopotamus



Indricotherium’s closest living relative is the rhinoceros.


Indricotherium’s closest living relative is the rhinoceros.


This endangered mammal species is covered with scales made from keratin. What is it?

  • armadillo
  • aardvark
  • pangolin



If frightened, pangolins can roll up and extend their scales into a phalanx of sharp blades.


The correct answer is pangolin.


Now extinct, glyptodonts were covered with thick armor made from bony plates that grew from within their skin. What did they eat?

  • plants
  • insects
  • small rodents



For millions of years, this enormous mammal lumbered across North and South America eating plants.


The correct answer is plants.

You correctly answered out of 9 questions. A total of participants have so far averaged correct answers.


Indy Tours San Francisco


Indy has had a wonderful time touring San Francisco. She's found one place that she's grown a particular attachment to - the Academy. Come see her featured in Extreme Mammals at the Academy until September 12, 2010.

See Indy’s photo album


Create Your Own

Click here to download a file to add Indy into your own images (through Photoshop only). Post your photos on Flickr and tag them “indytourssf” & we’ll share them below.

Photo of Indy: © AMNH/D. Finnin


Indy Sightings

Download the free Flash player from Adobe.

Extreme Life
Scavenger Hunt


Extend your visit to the Extreme Mammals exhibit by discovering the variety of exceptional animals and plants found throughout our museum. Pick one up in the Naturalist Center or download it here. Available in English and Spanish.

Answer keys are also available in English and Spanish.