Cervus canadensis (North American elk) (Rocky Mountains National Park, Colorado, USA) 10 : 無料・フリー素材/写真
Cervus canadensis (North American elk) (Rocky Mountains National Park, Colorado, USA) 10 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | Cervus canadensis (Erxleben, 1777) - female North American elk in Colorado, USA (boreal summer 2009).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.Shown above is a female North American elk. During boreal summers, female elk (cows) herd together while grazing in the mountains. They average about 500 pounds in size.Classification: Animalia, Chordata, Vertebrata, Mammalia, Artiodactyla, CervidaeLocality: Trail Ridge, near Forest Canyon overlook, Rocky Mountains National Park, northern Colorado, USA |
| 撮影日 | 2009-07-26 14:22:34 |
| 撮影者 | James St. John |
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