Portal:Mammals

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Mammals

Dwarf mongoose Korkeasaari zoo.jpg

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.

Nuvola filesystems www.png Mammals ...

Selected article

Cervus canadensis
The elk, or wapiti (Cervus canadensis), is the second largest species of deer in the world and one of the largest mammals in North America and eastern Asia. In the deer family (Cervidae), only the moose, Alces alces (called an "elk" in Europe), is larger. Wapiti are almost identical to red deer found in Europe, of which they were long believed to be a subspecies; they have recently been determined to be a distinct species based on DNA evidence. Elk range in forest and forest-edge habitat, feeding on grasses, plants, leaves and bark. Although native to North America and eastern Asia, they have adapted well to countries where they have been introduced, including New Zealand and Argentina. Their high level of adaptability poses a threat to endemic species and ecosystems where they have been introduced. Male elk have large antlers which are shed each year. Males engage in ritualized mating behaviors during the rut, including posturing, antler wrestling and bugling, a loud series of screams which establishes dominance over other males and attracts females. The bugle call is one of the most distinctive calls in nature. Elk are susceptible to a number of infectious diseases, some of which can be transmitted to livestock. Efforts to eliminate infectious diseases from elk populations, largely through vaccination, have had mixed success. Some cultures revere the elk as a spiritual force. In parts of Asia, antlers and their velvet are used in traditional medicines. Elk are hunted as a game species; the meat is leaner and higher in protein than beef or chicken.

Did you know?

Caracal001.jpg
  • ....that Caracal (pictured) is very powerful for its size and has even been known to bring down a full grown adult Gazelle?
  • ...that Snuppy the Afghan Hound is the world's first cloned dog?
  • ...the male narwhal's tusk can be up to 3 metres in length and weigh up to 10 kilograms?
  • ...the Voyager Golden Record carried into space whale songs, among other sounds?
  • ...that 217 Dalmatians were used in the filming of 101 Dalmatians?
  • ...that Scarlett the cat is a former stray cat whose efforts to save her kittens from a fire, at serious harm to herself, attracted worldwide media attention and has been related in a number of nonfiction books?
  • ...that Dr. Johnson's cat Hodge has his own statue in Gough Square, London?

Selected picture

Otters
Credit: Dmitry Azovtsev

The Otter (Lontra canadensis) is a North American member of the Mustelidae or weasel family. It is also known as the North American River Otter. It is a common animal in North American waterways. Its numbers have significantly dropped since Europeans came to colonize the Americas

Scientific classification

KingdomAnimalia   PhylumChordata   SubphylumVertebrata   SuperclassTetrapoda   (unranked)Amniota   ClassMammalia


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