In terms of cladistics, which reflects evolutionary history, mammals are the only living members of the Synapsida; this clade, together with Sauropsida (reptiles and birds), constitutes the larger Amniota clade. The early synapsid mammalian ancestors were sphenacodontpelycosaurs, a group that included the non-mammalian Dimetrodon. At the end of the Carboniferous period around 300 million years ago, this group diverged from the sauropsid line that led to today's reptiles and birds. The line following the stem group Sphenacodontia split into several diverse groups of non-mammalian synapsids—sometimes incorrectly referred to as mammal-like reptiles—before giving rise to Therapsida in the Early Permian period. Mammals originated from cynodonts, an advanced group of therapsids, during the Late Triassic. The modern mammalian orders arose 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 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 cohort 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, and echolocation. 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, 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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The Island Fox ( Urocyon littoralis) is a small fox that is native to six of the eight Channel Islands of California. It is the smallest fox species in the United States. There are six subspecies of the fox, each unique to the island it inhabits, reflecting its evolutionary history. Other names for the Island Fox include Coast Fox, Short-Tailed Fox, Island Gray Fox, Channel Islands Fox, Channel Islands Gray Fox, California Channel Island Fox and Insular Gray Fox. The Island Fox shares the Urocyongenus with the mainland Gray Fox, the fox from which it is descended. Its small size is a result of island dwarfing, a kind of allopatric speciation. Because Island Foxes are geographically isolated they have no immunity to parasites and diseases brought in from the mainland and are especially vulnerable to those domestic dogs may carry. In addition, Golden Eagle predation and human activities devastated fox numbers on several of the Channel Islands in the 1990s. Four Island Fox subspecies were federally protected as an endangered species in 2004, and efforts to rebuild fox populations and restore the ecosystems of the Channel Islands are being undertaken.
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...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 was a cat named Tama?
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Tamias rufus
Photo credit: Mdf
The Hopi Chipmunk (Tamias rufus) is a chipmunk found in Colorado, Utah and New Mexico, in the Southwestern United States. Chipmunks are small squirrel-like rodents, native to North America except for one species in northeastern Asia. Though they are commonly depicted with their paws up to the mouth, eating peanuts, or with their cheeks bulging out on either side, chipmunks are actually omnivorous.
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Common Brushtail Possum
Photo: JJ Harrison
The Common Brushtail Possum (Trichosurus vulpecula) is the largest possum species and is perhaps the most widespread mammal in Australia. It grows to about 32–58 cm (13–23 in) in length, with an additional 24–40 cm (9–16 in) for its prehensile tail (seen here hanging below the branch). It is mainly a folivore, but has been known to eat small mammals such as rats. It is common in cities, having adapted well to human habitation.
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Eastern gray squirrel
Photograph credit: Tom Friedel
The eastern gray squirrel (Sciurus carolinensis) is a tree squirrel in the genus Sciurus, native to the eastern and midwestern United States, as well as to the southerly portions of the eastern provinces of Canada. A prolific and adaptable species, it has been introduced to and thrives in several regions of the western United States; it is also an invasive species in Britain, where it has spread across the country and largely displaced the native Eurasian red squirrel. The head and body can measure from 23 to 30 cm (9.1 to 11.8 in) and the tail from 19 to 25 cm (7.5 to 9.8 in) in length; its adult weight is between 400 and 600 g (14 and 21 oz). Like many members of the family Sciuridae, the eastern gray squirrel is a scatter-hoarder; it hoards food in numerous small caches for later recovery. In the United Kingdom and Canada, the species is simply referred to as the "grey squirrel".
This picture, taken in 2010, shows an eastern gray squirrel in Florida.
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Impala
Photograph: Muhammad Mahdi Karim
A portrait of a male impala, showing its horns. Horns consist of bone cores surrounded by a covering of keratin and other proteins, and are often curved or spiral in shape. Most horned animal species have one pair, though some may have more.
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Prairie dog
Photo credit: Aaron Siirila
A black-tailed prairie dog at the National Zoo in Washington, D.C., looks out from a system of burrows, characteristically scanning the horizon. On average, these rodents grow to between 12 and 16 inches (30 and 40 cm) long, including their short tails.
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Sahelanthropus tchadensis
Photo: Didier Descouens
A cast of the extinct hominid species Sahelanthropus tchadensis holotype cranium, dubbed "Toumaï", in facio-lateral view. The original cranial fragment is dated to about 7 million years ago and was discovered in Chad. Other than Toumaï, the only Sahelanthropus remains to be discovered are five pieces of jaw and some teeth.
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Impala
Photo: Ikiwaner
The impala (Aepyceros melampus) is a medium-sized African antelope. The name comes from the Zulu language. They are normally reddish-brown, with lighter flanks, white underbellies, and a characteristic "M" marking on the rear. Males have lyre-shaped horns, which can reach up to 90 cm (35 in) in length. They are strong jumpers, able to reach distances more than 10 m (33 ft) in a single bound. They are also fast runners, capable of reaching speeds up to 90 km/h (56 mph).
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Southern Elephant Seal
Photo: Serge Ouachée
Close-up of a juvenile Southern Elephant Seal (Mirounga leonina), showing face and mouth detail. This species of elephant seal is not only the most massive pinniped, but also the largest member of the order Carnivora living today. It is found throughout the subantarctic region.
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Northern Elephant Seals
Photo credit: Helen Filatova
A group of female Northern Elephant Seals (Mirounga angustirostris) moulting on a beach near San Simeon, California. In the summer, elephant seals undergo a catastrophic moult, lasting about one month, during which they lose much of their fur and skin. They spend this time on beaches to preserve body heat, while they wait for the new fur to grow.
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Goat kid
Photo credit: Fir0002
A 2-month old domestic goat (Capra aegagrus hircus) kid in a field of capeweed. Goats are one of the oldest domesticated species. For thousands of years, goats have been used for their milk, meat, hair, and skins over much of the world. Female goats are referred to as does or nannies, intact males as bucks or billies; their offspring are kids.
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Impala
Photo: Alchemist-hp
Several female black-faced impala drinking at a waterhole. Impalas are sexually dimorphic. Females can weigh 10 to 25 kilograms (22 to 55 lb) less than males and do not have horns.
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Hoffmann's two-toed sloth
Photograph: Geoff Gallice
Hoffmann's two-toed sloth (Choloepus hoffmanni) is a species of sloth from Central and South America named for the German naturalist Karl Hoffmann. This solitary, largely nocturnal and arboreal animal, is found in mature and secondary rainforests and deciduous forests. Adults range from 54 to 72 cm (21 to 28 in) in head-body length, and weigh from 2.1 to 9 kg (4.6 to 19.8 lb). Females are larger on average than males, although with considerable overlap in size.
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Giraffe
Photo: Muhammad Mahdi Karim
A giraffe extending its tongue to feed. Its tongue, lips and palate are tough enough to deal with sharp thorns in trees. Giraffes prefer trees of the genera Acacia, Commiphora and Terminalia. A giraffe requires less food than typical grazing animals, typically consuming 65 pounds (29 kg) of leaves and twigs daily, because the foliage it eats has more concentrated nutrition and it has a more efficient digestive system.
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Joey
Photo credit: Geoff Shaw, University of Melbourne, Australia
A newborn joey (baby kangaroo) in its mother's pouch. Kangaroo babies are born at a very early stage of development after a gestation of 31-36 days. At this stage, only the forelimbs are somewhat developed, to allow the newborn to climb to the pouch and attach to a teat. It will not re-emerge for several months, during which time it develops fully.
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Pantanal jaguar
Photograph: Charles J. Sharp
A wild male jaguar (Panthera onca) near the Rio Negro in the Pantanal, Brazil. Jaguars from the Pantanal are the largest of their species, about 2.7 m (8.9 ft) long, with an average weight of about 100 kg (220 lb), and some weighing more than 135 kg (298 lb). A red jaguar was a mascot of the 1968 Summer Olympics in Mexico City, and during the 2016 Summer Olympics, a jaguar in the national colors of green and yellow was the Brazil team's mascot.
File:Sidney Hall - Urania's Mirror - Ursa Major.jpg
File:South-western black rhinoceros (Diceros bicornis occidentalis) female.jpg
File:Spotted hyena (Crocuta crocuta).jpg
File:Topi (Damaliscus lunatus jimela) female.jpg
File:Tragelaphus strepsiceros ♂ (head).jpg
File:Ugandan kobs (Kobus kob thomasi) female and calf.jpg
File:Vombatus ursinus -Maria Island National Park.jpg
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Wilson & Reeders Mammal Species of the World – from Bucknell University
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