North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea.
North America covers an area of about 24,709,000 square kilometers (9,540,000 square miles), about 4.8% of the planet's surface or about 16.5% of its land area. As of July 2008, its population was estimated at nearly 529 million people across 23 independent states, representing about 7.5% of the human population. Most of the continent's land area is dominated by Canada, the United States, and Mexico, while smaller states exist in the Central American and Caribbean regions. North America is the third-largest continent by area, following Asia and Africa, and the fourth by population after Asia, Africa, and Europe.
The Hystricognathi are an infraorder of rodents, distinguished from other rodents by the bone structure of their skulls. The masseter medialis (a jaw muscle) passes partially through the infraorbital foramen and connects to the bone on the opposite side. This, together with their lack of an infraorbital plate and the relative size of the infraorbital foramen, distinguishes hystricognaths from other rodent groups.
The fur trade is a worldwide industry dealing in the acquisition and sale of animal fur. Since the establishment of a world fur market in the early modern period, furs of boreal, polar and cold temperate mammalian animals have been the most valued. Historically the trade had a large impact on the exploration and colonization of Siberia, northern North America and the South Shetland and South Sandwich Islands. Today the importance of the fur trade has diminished and is currently centered around fur farms and regulated furbearer trapping, but remains controversial. Several animal rights organizations oppose the fur trade, while supporters often cite their methods as not being cruel, that the animal populations are abundant, and their rights to practice a traditional lifestyle should be respected. The use of fur has been partly substituted by synthetic imitations.
The Chacoan mara, Dolichotis salinicola, is a relatively large rodent from South America of the cavy family. They are a close relative of the better known Patagonian mara.
Neochoerus pinckneyi was a North American species of capybara. While capybaras originated in South America, formation of the Isthmus of Panama three million years ago allowed some of them to migrate north as part of the Great American Interchange. Capybaras and porcupines are the only caviomorph rodents that reached temperate North America during this exchange (a much greater diversity of North American rodents invaded South America). At 90 to 113 kg (200 to 250 pounds), 40% larger than the living capybara, N. pinckneyi is one of the largest rodent species ever discovered, surpassed only by the recently discovered Josephoartigasia monesi, several species of Phoberomys, and possibly the Pleistocene giant beaver. Remains have been found in southern North America and throughout Central America. During the Pleistocene, they extended their range, from Arizona to Florida to South Carolina.
The fauna of South America consists of a huge variety of unique animals some of which evolved in relative isolation. The isolation of South America had an abrupt end some few million years ago when the Isthmus of Panama was formed allowing small scale migration of animals that would result in the Great American Interchange.
Some examples of animals in South America appear below: