Guiana-Brazilian Subregion

the largest of the sub-regions of the Neotropical zoogeographic land region. The Guiana-Brazilian subregion occupies the entire northern part of South America, extending south almost to the Tropic of Capricorn. The high mountains and western slopes of the Andes (south of 5° S lat.) are usually not included in the subregion.

The Guiana-Brazilian subregion, which is almost entirely forest country, is the largest area of tropical rain forests in the world. Its center and its most typical territory is the Amazon Basin, as well as the basins of the Orinoco and the upper reaches of the Paraná. Mountains occupy a comparatively small area of the subregion. The small steppe area is located primarily in the south.

The fauna of the Guiana-Brazilian subregion is distinguished by its great abundance and variety. (The subregion is the richest faunal territory on the globe.) This is explained by the optimal conditions of existence and the ancient origins of the fauna. Certain features of fauna of the Miocene period that are usually found in nontropical fauna are represented in their clearest form in the Guiana-Brazilian subregion. Adaptation of various groups to life in trees is characteristic, and the degree of specialization in this respect is very high —sometimes extreme (for example, among sloths). Endemism is evident in all groups and is even characteristic of large taxonomie categories. Among mammals, various platyrhine monkeys (marmosets, tamarins, and howler monkeys), sloths, and two species of tapirs are most common and mostly endemic. Among the predators in the subregion are coatis, kinkajous (the strong-tailed “bear”), and bushdogs. Other animals include armadillos (including the giant armadillo) and many genera and species of bats (including vampire bats) and rodents (in particular, a special genus of agouti, the capybara, tree porcupines, and many species of squirrels). River dolphins and one species of freshwater amazonian manatee are common. Birds are even more numerous and varied than animals, and almost one-fifth of the genera are endemic. Various types of parrots, woodpeckers, toucans, hummingbirds, and hoatzins are common.

Snakes and lizards are numerous and to a large extent endemic. Among them are many tree types—for example, from the family Iguanidae. Boa constrictors are common, including the largest of all present-day snakes—the water anaconda. There are several species of crocodile. Frogs belonging to several families are numerous, including many that live in trees. The Surinam toad is typical. Among the many endemic freshwater fish, the most interesting are the dipnoan lungfish, the electric eel, and the largest of the freshwater bony fishes—the arapaima.

The fauna of the Guiana-Brazilian subregion has certain features in common with the fauna of the forest regions of Africa, Madagascar, the Malayan archipelago, and Australia. These features are vestiges of the links among the ancient Tertiary forest fauna of the tropical belt of the earth.