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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. The Tasmanian Devil (Sarcophilus harrisii), also referred to simply as 'the devil', is a carnivorous marsupial now found in the wild only in the Australian island state of Tasmania. The Tasmanian Devil is the only extant member of the genus Sarcophilus. The size of a small dog, but stocky and muscular, the Tasmanian Devil is now the largest carnivorous marsupial in the world (after the recent extinction of the Thylacine in 1936). It is characterised by its black fur, offensive odour when stressed, extremely loud and disturbing screech, and viciousness when feeding. It is known to both hunt prey and scavenge carrion and although it is usually solitary, it sometimes eats with other devils. The Tasmanian Devil became extirpated on the Australian mainland about 400 years before European settlement in 1788. Because they were seen as a threat to livestock in Tasmania, devils were hunted until 1941, when they became officially protected. Since the late 1990s devil facial tumour disease has reduced the devil population significantly and now threatens the survival of the species, which may soon be listed as endangered. Programs are currently being undertaken by the Tasmanian government to reduce the impact of the disease. ...that one burrow of the eastern chipmunk (pictured) was found to contain 390 acorns? .. that the Hare Indian dog, now extinct, was not known to bark, but puppies learned to imitate the barking of other dogs when the breed was introduced to Europe? ... that the rodents Thomasomys ucucha from Ecuador and Oxymycterus hucucha from Bolivia were both named after the local Quechua word for "mouse"? ...that the incisors of blesmols are visible even when their mouths are closed? ... that the pebble-mound mice of northern Australia construct mounds of stones around their burrows up to 10 m2 in area? ... that the stationmaster of the Kinokawa train station in Kinokawa, Japan is a cat named Tama? The Harbor seal or Common seal (Phoca vitulina) is a true seal of the Northern Hemisphere. Having the widest range of all pinnipeds, Harbor seals are found in coastal waters of the northern Atlantic and Pacific Oceans as well as those of the Baltic and North Seas. Monotremata Didelphimorphia Paucituberculata Microbiotheria Notoryctemorphia Dasyuromorphia Peramelemorphia Diprotodontia Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia Cingulata Pilosa Scandentia Dermoptera Primates Rodentia Lagomorpha Erinaceomorpha Soricomorpha Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Biology Tree of Life Prokaryotes and Protists Plants Arthropods Cephalopods Gastropods Fishes Amphibians and Reptiles Birds Mammals WikiProject Dogs WikiProject Dog breeds WikiProject Rodents WikiProject Cats WikiProject Equine WikiProject Horse breeds WikiProject Cetaceans WikiProject Primates WikiProject Monotremes and Marsupials Viruses A complete list of scientific WikiProjects can be found here. See also Wikispecies, a Wikimedia project dedicated to classification of biological species. Articles needing attention Biology pages needing attention (cleanup, expansion, wikification, expert needed, etc.) Help Wikipedia by uploading required images Help Wikipedia by creating pages or redirects Help Wikipedia by expanding mammal-related stub articles. Biology • Agriculture and Agronomy • Animals  • Arthropods • Amphibians and Reptiles • Biotechnology • Birds • Cats • Cetaceans • Dinosaurs • Dogs • Extinct and Endangered Species • Evolutionary biology • Fish • Marine life • Medicine • Metabolism • Mind and Brain • Molecular and Cellular Biology • Neuroscience • Plants • Primates • Sharks • Turtles What are portals? List of portals Featured portals