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 humpback whale (Megaptera novaeangliae) is a baleen whale. One of the larger rorqual species, adults range in length from 12–16 metres (40–50 ft) and weigh approximately 36,000 kilograms (79,000 lb). The humpback has a distinctive body shape, with unusually long pectoral fins and a knobbly head. It is an acrobatic animal, often breaching and slapping the water. Males produce a complex whale song, which lasts for 10 to 20 minutes and is repeated for hours at a time. The purpose of the song is not yet clear, although it appears to have a role in mating. Found in oceans and seas around the world, humpback whales typically migrate up to 25,000 kilometres each year. Humpbacks feed only in summer, in polar waters, and migrate to tropical or sub-tropical waters to breed and give birth in the winter. During the winter, humpbacks fast and live off their fat reserves. The species' diet consists mostly of krill and small fish. Humpbacks have a diverse repertoire of feeding methods, including the spectacular bubble net feeding technique.
Drymoreomys is a genus of South American rodent represented by a single species, D. albimaculatus. First formally described in 2011, the species prefers dense, moist, montane and premontane forest. Morphological evidence suggests they are tree dwellers.
The term African elephant refers to elephants of the genus Loxodonta. Shown here is the African bush elephant (Loxodonta africana), one of two extant species and the largest living terrestrial animal, with males standing 3.2–4.0 m (10.5–13.1 ft) tall at the shoulder and weighing 4,700–6,048 kg (10,362–13,334 lb).
A female Parma Wallaby (Macropus parma) and her joey. This wallaby species is the smallest member of the genus Macropus, at between 3.2 and 5.8 kilograms (7.1 and 12.8 lb) and about 50 centimetres (1.6 ft) in length. It was believed to be extinct before the end of the 19th century, but a population was found on Kawau Island in 1965, and two years later another population was found in the forests near Gosford, New South Wales. They are now classified as Near Threatened.
Two pot-bellied pigs sleeping. This breed of domestic pig belongs to the same species as the Wild Boar and the common farm pig (Sus domestica), and originated in Vietnam. Most adult pot-bellied pigs are about the size of a medium- or large-breed dog, though their bodies are denser at a weight of 60 to 300 pounds (27 to 136 kg).
The European wildcat (Felis silvestris silvestris) is a subspecies of the wildcat. It is native to the forests and grasslands of Europe, as well as Turkey and the Caucasus Mountains. Bulkier than both the African wildcat and the domestic cat, the European wildcat is also distinguished by its thick fur and non-tapered tail. Though it is predominantly nocturnal, the European wildcat may be active in the daytime in the absence of humans.
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.
An adult and a juvenile olive baboon (Papio anubis) at Queen Elizabeth National Park, Uganda. The most wide-ranging of all baboons, the olive baboon inhabits savannas, steppes, and forests in 25 countries throughout Africa. This highly adaptable species is omnivorous, feeding on a large variety of plants, invertebrates, small mammals, and birds.
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 Africa, Asia and Europe, lions presently exist in the wild only in Africa and India.
A portrait of a snow leopard (Panthera uncia) at the Rheintal Zoo in Germany. This species of big cat in the genusPanthera is native to the mountain ranges of Central and South Asia. The snow leopard's adaptations for life in a cold, mountainous environment include a stocky body, thick fur, small rounded ears to minimize heat loss, and a short muzzle with unusually large nasal cavities that help the animal breathe the cold, thin air.
The brown-throated sloth (Bradypus variegatus) is the most common species of three-toed sloth. It is found in the forests of South and Central America. Males and females are both about 42–80 cm (17–31 in) in total body length and weigh 2.25–6.3 kg (5–14 lb).
The European hedgehog (Erinaceus europaeus) is a species of hedgehog found in a wide range of habitat types in western Europe. It is a well-known species, and a favourite in European gardens, both for its endearing appearance and its preference for eating a range of garden pests. While populations are currently stable across much of its range, it is thought to be declining severely in Great Britain.