In the evolutionary history of animals, mammals occupy a very important position.

Recently, an amazing exhibition named 鈥淓xtreme Mammals: the Biggest, Smallest, and Most Amazing Mammals of All Time鈥?is held by California Academy of Sciences in San Francisco.

It is a pity that most of those mammals which were displayed at the exhibition have already died out. Following are some of those fantastic mammals.

Saber-Toothed Cat (Photo Source: www.xinhuanet.com)