Bison bison (Linnaeus, 1758) - American plains buffalo in South Dakota, USA (August 2010).
Mammals are the dominant group of terrestrial vertebrates on Earth today. The group is defined based on a combination of features: endothermic (= warm-blooded), air-breathing, body hair, mother's milk, four-chambered heart, large brain-to-body mass ratio, two teeth generations, differentiated dentition, and a single lower jawbone. Almost all modern mammals have live birth - exceptions are the duck-billed platypus and the echidna, both of which lay eggs.
Mammals first appear in the Triassic fossil record - they evolved from the therapsids (mammal-like reptiles). Mammals were mostly small and a minor component of terrestrial ecosystems during the Mesozoic. After the Cretaceous-Tertiary mass extinction at 65 million years ago, the mammals underwent a significant adaptive radiation - most modern mammal groups first appeared during this radiation in the early Cenozoic (Paleocene and Eocene).
Three groups of mammals exist in the Holocene - placentals, marsupials, and monotremes. Other groups, now extinct, were present during the Mesozoic.
The American buffalo was formerly hyperabundant in western America. It was driven nearly to extinction by tribal American Indians and colonial Americans. The sizable population resulted from the species expanding into empty niche space after the end-Pleistocene mass extinction of large North American megafauna (e.g., mammoths, mastodons, etc.). The mass extinction was due to a combination of climate warming (= end of the Wisconsinan Ice Age) and overhunting by American Paleoindians.
Classification: Animalia, Chordata, Vertebrata, Mammalia, Artiodactyla, Bovidae
Locality: Wind Cave National Park, southern Black Hills, southwestern South Dakota, USA
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See info. at:
en.wikipedia.org/wiki/American_bison
and
en.wikipedia.org/wiki/Plains_bison
and
en.wikipedia.org/wiki/Bison
