Mesonychia is an extinct taxon of small- to large-sized carnivorous ungulates related to artiodactyls. Mesonychids first appeared in the early Paleocene, went into a sharp decline at the end of the Eocene, and died out entirely when the last genus, Mongolestes, became extinct in the early Oligocene. In Asia, the record of their history suggests they grew gradually larger and more predatory over time, then shifted to scavenging and bone-crushing lifestyles before the group became extinct.
Sparassodonta is an extinct order of carnivorous metatherian mammals native to South America, related to modern marsupials. They were once considered to be true marsupials, but are now thought to be a separate side branch that split before the last common ancestor of all modern marsupials. A number of these mammalian predators closely resemble placental predators that evolved separately on other continents, and are cited frequently as examples of convergent evolution. They were first described by Florentino Ameghino, from fossils found in the Santa Cruz beds of Patagonia. Sparassodonts were present throughout South America's long period of "splendid isolation" during the Cenozoic; during this time, they shared the niches for large warm-blooded predators with the flightless terror birds. Previously, it was thought that these mammals died out in the face of competition from "more competitive" placental carnivorans during the Pliocene Great American Interchange, but more recent research has showed that sparassodonts died out long before eutherian carnivores arrived in South America. Sparassodonts have been referred to as borhyaenoids by some authors, but currently the term Borhyaenoidea refers to a restricted subgroup of sparassodonts comprising borhyaenids and their close relatives.
Pyrotheria is an order of extinct meridiungulate mammals. These mastodon-like ungulates include the genera Baguatherium, Carolozittelia, Colombitherium, Griphodon, Propyrotherium, Proticia, and Pyrotherium.
Xenungulata is an order of extinct and primitive South American hoofed mammals that lived from the Late Paleocene to Early Eocene. Fossils of the order are known from deposits in Brazil, Argentina, Peru, and Colombia. The best known member of this enigmatic order is the genus Carodnia, a tapir-like and -sized animal with a gait similar to living African elephants.
Pyrotherium is an extinct genus of South American ungulate, of the order Pyrotheria, that lived in what is now Argentina and Bolivia, during the Late Oligocene. It was named Pyrotherium because the first specimens were excavated from an ancient volcanic ash deposit. Fossils of the genus have been found in the Deseado and Sarmiento Formations of Argentina and the Salla Formation of Bolivia.
Carodnia is an extinct genus of South American ungulate known from the Early Eocene of Brazil, Argentina, and Peru. Carodnia is placed in the order Xenungulata together with Etayoa and Notoetayoa.
Coloniatherium is a meridiolestid mammal from the Late Cretaceous of Argentina. The single species, Coloniatherium cilinskii, was a large member of the family Mesungulatidae.
The Río Loro Formation is a geological formation of the Sierras Pampeanas in Tucumán Province Argentina whose strata date back to the Late Paleocene of the Paleogene, or Riochican in the SALMA classification.
Bemalambda is an extinct mammal, belonging to the pantodonts. It lived in the lower-middle Paleocene and the fossil remains have been found in China.
Ernestokokenia is an extinct genus of mammal, belonging to the Didolodontidae. It lived during the Early Eocene and the Middle Eocene, and its fossils were discovered in South America.
Notoetayoa is an extinct genus of mammal, from the order Xenungulata. It contains a single species, Notoetayoa gargantuai, which lived during the Middle Paleocene. Its fossilized remains were discovered in South America.
Eoastrapostylops is an extinct genus of astrapothere that lived during the Late Paleocene in what is now Argentina.
Propyrotherium is an extinct genus of mammals, belonging to the order Pyrotheria. It lived during the Late Eocene, in what is now South America.
Notonychops is an extinct genus of mammal, belonging to the order Litopterna, that lived during the Middle to Late Paleocene in what is today South America.
Prolicaphrium is an extinct genus of proterotheriid litoptern that lived during the Early Miocene, in what is now Argentina. Fossils have been found in the Sarmiento Formation of Argentina.
Henricosbornia is an extinct genus of henricosborniid notoungulate that lived from the Late Paleocene to the Middle Eocene of what is now Argentina and Brazil.
Colpodon is an extinct genus of herbivorous mammal, belonging to the order Notoungulata. It lived during the Early Miocene, in what is today Argentina and Chile, in South America.
Archaeopithecus is an extinct genus of Notoungulate, belonging to the suborder Typotheria. It lived during the Middle Eocene, in what is today Argentina.
Oldfieldthomasia is an extinct genus of Notoungulate, probably related to the suborder Typotheria. It lived during the Middle Eocene, in what is today South America.
Archaeogaia is an extinct genus of notoungulates that lived during the Early and Middle Paleocene of what is now Argentina. It is one of the oldest known unequivocal notoungulates.
