User:Abyssal/Prehistory of South America

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The Prehistory of South America Portal

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Introduction

The Prehistory of South America portal collects and presents articles, images and categories on the prehistorical period in time (before 10,000 years ago) of the continent South America. South America has a rather unique prehistory, both regarding the human settlement prehistory and early history and the flora and fauna prehistory of the continent. For approximately 115 million years, since the Aptian, the continent was no longer connected to Africa and the other landmasses of Eurasia and North America and during the early Cenozoic, the continent became unconnected to Australia. The only connection to another continent was with Antarctica, that drifted away in the late Eocene, approximately 35 million years ago.

The next 30 million years, until the late Miocene to early Pliocene (6-4 million years ago), South America was completely isolated from the other landmasses, separated by the Atlantic, Pacific, Antarctic and paleo-Caribbean oceans. This caused the evolution of a unique prehistoric fauna and flora in South America. Due to plate tectonic movements in the Neogene, the isthmus of Panama was formed, leading to the Great American Biotic Interchange (GABI), drastically reshaping the faunal assemblages of both Americas, but South America in particular, with many more migration from north to south than vice versa.

The history of human settlement was equally recent, with the oldest evidences dating to approximately 18,500 years ago (Monte Verde, Chile). Human migration resembled the migration of prehistoric animals; via the Isthmus of Panama, arriving first in what is now Colombia. The indigenous people spread out across the continent with hunter-gatherer lifestyles. The human prehistory is followed by a period of sedentary settlement and the development of agriculture into various civilizations.

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Herrerasaurus was one of the earliest dinosaurs. Its name means "Herrera's lizard", after the rancher who discovered the first specimen. All known fossils of this carnivore have been discovered in rocks of Carnian age (late Triassic according to the ICS, dated to 231.4 million years ago) in northwestern Argentina. The type species, Herrerasaurus ischigualastensis, was described by Osvaldo Reig in 1963 and is the only species assigned to the genus. Ischisaurus and Frenguellisaurus are synonyms.

For many years, the classification of Herrerasaurus was unclear because it was known from very fragmentary remains. It was hypothesized to be a basal theropod, a basal sauropodomorph, a basal saurischian, or not a dinosaur at all but another type of archosaur. However, with the discovery of an almost complete skeleton and skull in 1988, Herrerasaurus has been classified as either an early theropod or an early saurischian in at least five recent reviews of theropod evolution, with many researchers treating it at least tentatively as the most primitive member of Theropoda.

It is a member of the Herrerasauridae, a family of similar genera that were among the earliest of the dinosaurian evolutionary radiation. (see more...)

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