Emperor penguin in the context of "Endemism in birds"

The wildlife of Antarctica are extremophiles, having adapted to the dryness, low temperatures, and high exposure common in Antarctica. The extreme weather of the interior contrasts to the relatively mild conditions on the Antarctic Peninsula and the subantarctic islands, which have warmer temperatures and more liquid water. Much of the ocean around the mainland is covered by sea ice. The oceans themselves are a more stable environment for life, both in the water column and on the seabed.

There is relatively little diversity in Antarctica compared to much of the rest of the world. Terrestrial life is concentrated in areas near the coast. Flying birds nest on the milder shores of the Peninsula and the subantarctic islands. Eight species of penguins inhabit Antarctica and its offshore islands. They share these areas with seven pinniped species. The Southern Ocean around Antarctica is home to 10 cetaceans, many of them migratory. There are very few terrestrial invertebrates on the mainland, although the species that do live there have high population densities. High densities of invertebrates also live in the ocean, with Antarctic krill forming dense and widespread swarms during the summer. Benthic animal communities also exist around the continent.

Penguins are a group of flightless, semi-aquatic, sea birds which live almost exclusively in the Southern Hemisphere. Only one species, the Galápagos penguin, lives at, and slightly north of, the equator. Highly adapted for life in the ocean water, penguins have countershaded dark and white plumage and flippers for swimming. Most penguins feed on krill, fish, squid and other forms of sea life which they catch with their bills and swallow whole while swimming. A penguin has a spiny tongue and powerful jaws to grip slippery prey.

They spend about half of their lives on land and the other half in the sea. The largest living species is the emperor penguin (Aptenodytes forsteri): on average, adults are about 1.1 m (3 ft 7 in) tall and weigh 35 kg (77 lb). The smallest penguin species is the little blue penguin (Eudyptula minor), also known as the fairy penguin, which stands around 30–33 cm (12–13 in) tall and weighs 1.2–1.3 kg (2.6–2.9 lb). Today, larger penguins generally inhabit colder regions, and smaller penguins inhabit regions with temperate or tropical climates. Some prehistoric penguin species were enormous: as tall or heavy as an adult human. There was a great diversity of species in subantarctic regions, and at least one giant species in a region around 2,000 km south of the equator 35 mya, during the Late Eocene, a climate decidedly warmer than today.

Palaeeudyptes klekowskii is an extinct species of the penguin genus Palaeeudyptes. It was previously thought to have been approximately the size of its congener Palaeeudyptes antarcticus, somewhat larger than the modern emperor penguin, but a 2014 study showed it was in fact almost twice as tall, earning it the nickname “Mega Penguin”. Its maximum length is estimated to be up to 2 meters (6.6 ft) and maximum body mass up to 116 kg (256 lb). Knowledge of it comes from an extensive collection of fossil bones from the Late Eocene (34-37 MYA) of the La Meseta Formation on Seymour Island, Antarctica. P. klekowskii was at first not recognized as a distinct species, and despite the coexistence of two so closely related species of similar size as Palaeeudyptes gunnari and P. klekowskii seeming somewhat improbable, the amount of fossil material suggests that the two species are indeed diagnosably different.

The Adélie penguin (Pygoscelis adeliae) is a species of penguin common along the entire coast of the Antarctic continent, which is the only place where it is found. It is the most widespread penguin species in the Antarctic, and, along with the emperor penguin, is the most southerly distributed of all penguins. It is named after Adélie Land, in turn, named for Adèle Dumont d'Urville, who was married to French explorer Jules Dumont d'Urville, who first discovered this penguin in 1840. Adélie penguins obtain their food by both predation and foraging, with a diet of mainly krill and fish.

The king penguin (Aptenodytes patagonicus) is the second largest species of penguin, smaller than but somewhat similar in appearance to the emperor penguin.

King penguins mainly eat lanternfish, squid, and krill. On foraging trips, king penguins repeatedly dive to over 100 metres (300 ft), and have been recorded at depths greater than 300 metres (1,000 ft). Predators of the king penguin include giant petrels, skuas, the snowy sheathbill, the leopard seal, and the orca.

Palaeeudyptes is an extinct genus of large penguins, currently containing four accepted species. They were probably larger than almost all living penguins, with the smaller species being about the size of an emperor penguin, and the largest species, Palaeeudyptes klekowskii, estimated to reach 2 meters (6.6 ft) long (measuring tip of beak to tail) and weighed up to 116 kg (256 lb).

Palaeeudyptes antarcticus, also referred to as the narrow-flippered penguin, is the type species of the extinct penguin genus Palaeeudyptes. It was a huge species, albeit probably with a large size variation. Although the size range can only be loosely estimated, the birds seem to have stood between 43 and 55 inches (1.1 and 1.4 m) high in life (i.e. somewhat larger than an emperor penguin), placing this species and its congener Palaeeudyptes marplesi among the largest penguin species known. It was the last known Palaeeudyptes species, and although the exact time when it lived is not precisely determined, it may have evolved from P. marplesi, or they might even have been a single species which slightly decreased in size over time.

P. antarcticus was the first fossil penguin to become known to science. It was described from a single, slightly damaged, tarsometatarsus (BM A.1084) found in the Late Oligocene Otekaike Limestone (23-28, possibly up to 34 MYA) at Kakanui, New Zealand. An older date seems quite possible in fact as other bones have now been recovered from the Late Eocene (34-37 MYA) of the La Meseta Formation on Seymour Island, Antarctica (Tambussi et al., 2006), but given the considerable distances in age and range involved, it is not completely certain that the bones belong to a single species.

Palaeeudyptes gunnari is an extinct species of the extinct penguin genus Palaeeudyptes. It was a bit smaller than its congener Palaeeudyptes antarcticus of New Zealand, standing between 110 and 125 cm high, approximately the size of the emperor penguin. It is known from dozens of fossil bones from Middle or Late Eocene strata (34-50 MYA) of the La Meseta Formation on Seymour Island, Antarctica. Initially, it was described as a separate genus, Eosphaeniscus. However, this was based on a single weathered and broken tarsometatarsus. Better material recovered later showed that the species belongs into the present genus.

Wimanornis is probably a synonym of this species (Jadwiszcak, 2006).