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Portal:Mammals

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Giraffe standing.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

Giant Otter
The Giant Otter (Pteronura brasiliensis) is an amphibious, mammalian carnivore native to South America. About the length of an adult human being, it is the longest member of the mustelidae, or weasel family, a globally successful group of predators. Unusually for a mustelid, the Giant Otter is a social species, with family groups typically supporting three to eight members. The groups are centred around a dominant breeding pair and are extremely cohesive and cooperative. Although generally peaceful, the species is territorial and aggression has been observed between groups. The Giant Otter is exclusively active during daylight hours. It is the noisiest otter species and distinct vocalizations have been documented that indicate alarm, aggressiveness, and reassurance. The Giant Otter ranges across north-central South America, although its distribution has been greatly reduced and is now discontinuous. The species was listed as endangered in 1999 and population estimates are typically below 5,000 in the wild. The Guianas are the last real stronghold for the species. Decades of poaching for its velvety pelt, peaking in the 1950s and 1960s, decimated population numbers. Habitat degradation and loss is the greatest current threat. The Giant Otter is also rare in captivity: as of 2003, only 60 animals were held.

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

Eastern Grey Squirrel in St James's Park, London
Credit: Diliff

An Eastern Gray Squirrel (Sciurus carolinensis) eating a nut in St. James's Park, London. Although native to eastern North America, the species has been introduced into a variety of locations. In England, gray squirrels have mostly replaced native Red Squirrels and have no natural predators, which has added to their rapid population growth and has led to the species being classed as a pest.

Scientific classification

KingdomAnimalia   PhylumChordata   SubphylumVertebrata   SuperclassTetrapoda   (unranked)Amniota   ClassMammalia


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