In terms of
cladistics, which reflects evolutionary history, mammals are the only living members of the
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
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 Herdwick is a traditional breed of
domestic sheep native to the mountainous
Lake District of
North West England. The name "Herdwick" is derived from the
Old Norseherdvyck, meaning sheep pasture. Though low in lambing capacity and wool quality when compared to more common commercial breeds such as
Merino sheep, Herdwicks are prized for their robust health, their ability to live solely on
forage, and their tendency not to stray over the difficult upland terrain of the Lake District. An integral part of the cultural identity of the Lake District, the breed is for the most part found in the central and western
dales of the region. Severely threatened by the
2001 outbreak of
foot-and-mouth disease in
Wales, the breed has survived due to the intent to preserve this unique animal as a crucial part of traditional Lakeland agriculture. Still far less in number than most commercial breeds, Herdwicks survive largely due to
farming subsidies and the aid of the British
National Trust for Places of Historic Interest or Natural Beauty.
...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?
A domesticated yak at
Yamdrok Lake in Tibet. The animals are important to Tibetan culture, and have been kept for thousands of years. The yaks are a method of transportation and serve as
beasts of burden. Their feces are a source of fuel, and their milk can be used for
butter, which is then made into
sculptures or consumed.
The Golden-mantled Ground Squirrel (Spermophilus lateralis) is a species of
squirrel native throughout
North America and can be found in a wide variety of forest habitats as well as rocky meadows, and even sagebrush flats. It can be identified by its
chipmunk-like stripes and coloration, but unlike chipmunks, it lacks any facial stripes.
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.
A male lion (Panthera leo) lying down in
Namibia. One of the four "
big cats" in the
genusPanthera, the lion is the second largest cat, after the
tiger. Males weigh between 150-250 kg (330-550 lb), and are easily recognizable by their manes. Though they were once found throughout much of
Europe, lions presently exist in the wild only in Africa and
A female koala (Phascolarctos cinereus), an
arborealherbivorousmarsupial native to coastal regions of eastern and southern Australia. The word "koala" comes from the
Dharuk word gula. English-speaking settlers from the late 18th century first called it "koala bear" due to its similarity in appearance to
bears, although they are not at all related. Instead, its closest living relative is the
Male lion (Panthera leo) and cub eating a
Cape Buffalo in Northern Sabi Sand,
South Africa. Lions are true
predators who can require an average of up to seven kilograms (15 lbs) of meat daily to survive. Large
mammals comprise an important part of a lion's diet.
The polar bear (Ursus maritimus) is a
hypercarnivorous bear whose native range lies largely within the
Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. A boar (adult male) weighs around 350–750 kilograms (770–1,650 lb), while a sow (adult female) is about half that size. Polar bears are the largest land carnivores currently in existence, rivalled only by the omnivorous
Kodiak bear. Although it is the
sister species of the
brown bear, it has evolved to occupy a narrower
ecological niche, with many body characteristics adapted for cold temperatures, for moving across snow, ice and open water, as well as for hunting
seals, which make up most of its diet. Although most polar bears are born on land, they spend most of their time on
sea ice. The species's scientific name, which is derived from this fact, means 'maritime bear'. Because of their dependence on sea ice, polar bears are categorized as
marine mammals. Due to expected
habitat loss caused by
global warming, the polar bear is classified as a
vulnerable species. For decades, large-scale hunting raised international concern for the future of the species, but populations have rebounded after controls and quotas began to take effect.
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
A wild male jaguar (Panthera onca) near the
Rio Negro in the
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.
The Tasmanian devil (Sarcophilus harrisii) is a
carnivorousmarsupial found in the wild only on the Australian island of
Tasmania. It is characterised by its stocky and muscular build, black fur, pungent odour, extremely loud and disturbing screech, keen sense of smell, and ferocity when feeding. Its large head and neck allow it to generate the strongest bite per unit body mass of any living mammal.
The European Hedgehog (Erinaceus europaeus) is a
hedgehog species native to western and northern Europe. Adults are 20–30 cm (7.9–11.8 in) in length, weighing from 600 to 1,200 g (21 to 42 oz), depending on the season, with males slightly larger than females. It is
nocturnal, and if alarmed will roll itself into a ball, protecting itself against potential
predators with its spines.
The skull of the African buffalo (Syncerus caffer), a large African bovine. It has a long but stocky body and short but thickset legs, resulting in a relatively short standing height. The adult bull’s horns, as shown here, have fused bases, forming a continuous bone shield known as a "boss".