File:Bison bison (American buffalo) (16 June 2023) (Upper Geyser Basin, Yellowstone, Wyoming, USA) 2.jpg

English: Bison bison (Linnaeus, 1758) - American buffalo in Wyoming, USA (June 2023).

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 large population resulted from the species expanding into a sizable and empty niche space after the end-Pleistocene mass extinction of large North American megafauna (e.g., mammoths, mastodons, etc.). The mass extinction occurred from a combination of climate warming (= end of the Wisconsinan Ice Age) and overhunting by American Paleoindians.

Wild buffalo are common in Yellowstone, Wyoming, but they represent the plains buffalo subspecies, which was introduced to Yellowstone, that has hybridized with the native woodlands subspecies (some dispute that account). Yellowstone buffalo are regularly "culled" / murdered by park personnel every spring, when the park is closed to the public, and by some Montana Indian tribes when buffalo leave the park during migrations.

Classification: Animalia, Chordata, Vertebrata, Mammalia, Artiodactyla, Bovidae

Locality: roadside, near Lower Hamilton Store, Upper Geyser Basin, Yellowstone, northwestern Wyoming, 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/Wood_bison and

en.wikipedia.org/wiki/Bison