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A mammal (from Latin mamma 'breast') is a vertebrate animal of the class Mammalia ( /məˈmli.ə/). Mammals are characterized by the presence of milk-producing mammary glands for feeding their young, a neocortex region of the brain, fur or hair, and three middle ear bones. These characteristics distinguish them from reptiles and birds, from which their ancestors diverged in the Carboniferous Period over 300 million years ago. Around 6,400 extant species of mammals have been described and divided into 29 orders.

The largest orders of mammals, by number of species, are the rodents, bats, and Eulipotyphla (including hedgehogs, moles and shrews). The next three are the primates (including humans, monkeys and lemurs), the even-toed ungulates (including pigs, camels, and whales), and the Carnivora (including cats, dogs, and seals).

Mammals are the only living members of Synapsida; this clade, together with Sauropsida (reptiles and birds), constitutes the larger Amniota clade. Early synapsids are referred to as " pelycosaurs". The more advanced therapsids became dominant during the Middle Permian. Mammals originated from cynodonts, an advanced group of therapsids, during the Late Triassic to Early Jurassic. Modern mammalian achieved their modern diversity in the Paleogene and Neogene periods of the Cenozoic era, after the extinction of non-avian dinosaurs, and have been the dominant terrestrial animal group from 66 million years ago to the present.

The basic mammalian body type is quadruped, and most mammals use their four extremities for terrestrial locomotion; but in some, the extremities are adapted for life at sea, in the air, in trees, underground, or on two legs. Mammals range in size from the 30–40 mm (1.2–1.6 in) bumblebee bat to the 30 m (98 ft) blue whale—possibly the largest animal to have ever lived. Maximum lifespan varies from two years for the shrew to 211 years for the bowhead whale. All modern mammals give birth to live young, except the five species of monotremes, which are egg-laying mammals. The most species-rich group of mammals, the infraclass called placentals, have a placenta, which enables the feeding of the fetus during gestation.

Most mammals are intelligent, with some possessing large brains, self-awareness, and tool use. Mammals can communicate and vocalize in several ways, including the production of ultrasound, scent-marking, alarm signals, singing, echolocation; and, in the case of humans, complex language. Mammals can organize themselves into fission–fusion societies, harems, and hierarchies—but can also be solitary and territorial. Most mammals are polygynous, but some can be monogamous or polyandrous.

Domestication of many types of mammals by humans played a major role in the Neolithic Revolution, and resulted in farming replacing hunting and gathering as the primary source of food for humans. This led to a major restructuring of human societies from nomadic to sedentary, with more co-operation among larger and larger groups, and ultimately the development of the first civilizations. Domesticated mammals provided, and continue to provide, power for transport and agriculture, as well as food ( meat and dairy products), fur, and leather. Mammals are also hunted and raced for sport, kept as pets and working animals of various types, and are used as model organisms in science. Mammals have been depicted in art since Paleolithic times, and appear in literature, film, mythology, and religion. Decline in numbers and extinction of many mammals is primarily driven by human poaching and habitat destruction, primarily deforestation. ( Full article...)

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Sumatran Rhinoceros
The Sumatran Rhinoceros (Dicerorhinus sumatrensis) is a species of the family Rhinocerotidae, and one of five extant rhinoceri. It is the smallest rhinoceros, standing about 120–145 centimetres (3.9–4.8 ft) high at the shoulder, with a body length of 250 centimetres (98 in) and weight of 500–800  kilograms (1100–1760 lb). Like its African counterparts, the black and white rhinoceri, it has two horns; the larger is the nasal horn, typically 15–25 centimetres (6–10 in), while the other is typically a stub. A coat of reddish-brown hair covers most of the rhino's body. Members of the species once ranged throughout rainforests, swamps and cloud forests in India, Bhutan, Bangladesh, Myanmar, Laos, Thailand, Malaysia, and Indonesia. They are now critically endangered, with only six substantial populations in the wild: four on Sumatra, one on Borneo, and one on peninsular Malaysia. Their numbers are difficult to determine because they are solitary animals that are widely scattered across their range, but they are estimated to number around just 300. The decline in the number of Sumatran rhinoceri is attributed primarily to poaching for their ivory horns, which are highly valued in traditional Chinese medicine, fetching as much as US$30,000 per kilogram on the black market. The rhinos have also suffered from habitat loss as their forests have been cleared for lumber and conversion to agriculture.

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Opposable 'thumb' on male polydactyl cat.
Opposable 'thumb' on male polydactyl cat.

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KingdomAnimalia   PhylumChordata   SubphylumVertebrata   SuperclassTetrapoda   (unranked)Amniota   Class Mammalia



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