Portal:Mammals

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Mammals

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Mammals (class Mammalia) are vertebrate animals characterized by the presence of sweat glands, including milk producing sweat glands, and by the presence of: hair, three middle ear bones used in hearing, and a neocortex region in the brain. Mammals, other than the monotremes, give birth to live young instead of laying eggs. They also possess specialized teeth and use a placenta in the ontogeny. The mammalian brain regulates endothermic and circulatory systems, including a four-chambered heart. Mammals encompass approximately 5,400 species, ranging in size from the Bumblebee Bat, (30-40mm), to the Blue Whale, (33,000mm), distributed in about 1,200 genera, 153 families, and 29 orders, though this varies by classification scheme.

Most mammals belong to the placental group. The four largest orders within the placental mammals are Rodentia (mice, rats, and other small, gnawing mammals), Chiroptera (bats), Carnivora (dogs, cats, bears, and other mammals that primarily eat meat), and Cetartiodactyla (including numerous herbivore species, such as deer, sheep, goats, and buffalos, plus whales).

Phylogenetically, Mammalia is defined as all descendants of the most recent common ancestor of monotremes (e.g., echidnas and platypuses) and therian mammals (marsupials and placentals). This means that some extinct groups of "mammals" are not members of the crown group Mammalia, even though most of them have all the characteristics that traditionally would have classified them as mammals. These "mammals" are now usually placed in the unranked clade Mammaliaformes.

The mammalian line of descent diverged from the sauropsid line at the end of the Carboniferous period. The sauropsids would evolve into modern-day reptiles and birds, while the synapsid branch led to mammals. The first true mammals appeared in the Jurassic period. Modern mammalian orders appeared in the Palaeocene and Eocene epochs of the Palaeogene period.

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Bobcat
The bobcat (Lynx rufus), occasionally known as the bay lynx, is a North American mammal of the cat family, Felidae. With twelve recognized subspecies, it ranges from southern Canada to northern Mexico, including most of the continental United States. The bobcat is an adaptable predator that inhabits wooded areas, as well as semi-desert, urban edge, and swampland environments. It persists in much of its original range and populations are healthy. With a gray to brown coat, whiskered face, and black-tufted ears, the bobcat resembles the other species of the mid-sized Lynx genus. It is smaller than the Canadian lynx, with which it shares parts of its range, but is about twice as large as the domestic cat. It has distinctive black bars on its forelegs and a black-tipped, stubby tail, from which it derives its name. Though the bobcat prefers rabbits and hares, it will hunt anything from insects and small rodents to deer and pronghorn antelope. Prey selection depends on location and habitat, season, and abundance. Like most cats, the bobcat is territorial and largely solitary, although there is some overlap in home ranges. It uses several methods to mark its territorial boundaries, including claw marks and deposits of urine or feces. The bobcat breeds from winter into spring and has a gestation period of about two months. Although the bobcat has been subject to extensive hunting by humans, both for sport and fur, its population has proven resilient. The elusive predator features in Native American mythology and the folklore of European settlers.

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Opposable 'thumb' on male polydactyl cat.

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Grizzly Bear
Credit: Jean-Pierre Lavoie/Fir0002

A Grizzly Bear (Ursus arctos horribilis) wandering in Denali National Park, Alaska during the autumn. The Grizzly Bear is a subspecies of the Brown Bear, found in the interior of North America. They reach weights of 180-680 kg (400-1,500 lb) and are colored blond to deep brown or black. In spite of their massive size, these bears can run at speeds of up to 55 km/h (35 mph). The current range of the Grizzly Bear extends from Alaska, down through much of Western Canada, and into the upper Northwestern United States including Idaho, Montana and Wyoming.

Scientific classification

KingdomAnimalia   PhylumChordata   SubphylumVertebrata   SuperclassTetrapoda   (unranked)Amniota   ClassMammalia


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