The opossum is a marsupial of the order Didelphimorphia endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 110+ species in 19 genera. Opossums originated in South America and entered North America in the Great American Interchange following the connection of the two continents. Their unspecialized biology, flexible diet, and reproductive habits make them successful colonizers and survivors in diverse locations and conditions.
Yalkaparidon is an extinct genus of Australian marsupials, first described in 1988 and known only from the Oligo-Miocene deposits of Riversleigh, northwestern Queensland, Australia.
Sparassodonta is an extinct order of carnivorous metatherian mammals native to South America. They were once considered to be true marsupials, but are now thought to be either a sister taxon to them, or far more distantly related, part of a separate clade of Gondwanan metatherians. 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.
Thylacosmilus is an extinct genus of saber-toothed metatherian mammals that inhabited South America from the Late Miocene to Pliocene epochs. Though Thylacosmilus looks similar to the "saber-toothed cats", it was not a felid, like the well-known North American Smilodon, but a sparassodont, a group closely related to marsupials, and only superficially resembled other saber-toothed mammals due to convergent evolution. A 2005 study found that the bite forces of Thylacosmilus and Smilodon were low, which indicates the killing-techniques of saber-toothed animals differed from those of extant species. Remains of Thylacosmilus have been found primarily in Catamarca, Entre Ríos, and La Pampa Provinces in northern Argentina.
Borhyaena is an extinct genus of South American metatherian, living between 17.5 and 15.5 million years ago in Patagonia, Argentina and Chile.
Borhyaenidae is an extinct metatherian family of low-slung, heavily built predatory mammals in the order Sparassodonta. Borhaenids are not true marsupials, but members of a sister taxon, Sparassodonta. Like most metatherians, borhyaenids and other sparassodonts are thought to have had a pouch to carry their offspring around. Borhyaenids had strong and powerful jaws, like those of the unrelated placentalians Hyaenodon and Andrewsarchus, for crushing bones. Borhyaenids grew up to an average of 5 to 6 feet long. Borhyaena is the type genus of this group.
La Venta is a fossil locality located in the modern departments of Tolima and Huila in Colombia. This site is one of the richest Neogene fossil assemblages in South America and represents the best-known Cenozoic fossil site outside of Argentina. It provides a glimpse of what life in the region was like before the main wave of the Great American Interchange.
Cyonasua is an extinct genus of procyonid from the Late Miocene to Middle Pleistocene of South America. Fossils of Cyonasua have been found in Argentina, Bolivia, Uruguay, and Venezuela. The oldest well-dated fossils of Cyonasua are approximately 7.3 million years old. Most fossils of Cyonasua are late Miocene to early late Pliocene in age, but a single early Pleistocene specimen indicates that members of this genus survived until at least 0.99 million years ago.
Hoazinoides is an extinct genus of birds from the Middle Miocene (Laventan) from the "Monkey Beds" of the Villavieja Formation of the Honda Group at the Konzentrat-Lagerstätte of La Venta, Colombia.
Langstonia is an extinct genus of notosuchian crocodylomorph of the family Sebecidae. It lived in the middle Miocene, in the "Monkey Beds" of the Colombian Villavieja Formation. Langstonia was named in 2007 by Alfredo Paolillo and Omar Linares for fossils originally described by Langston in 1965 as Sebecus huilensis. Thus, the type species is L. huilensis.(Paolillo & Linares 2007)
Anachlysictis gracilis is an extinct carnivorous mammal belonging to the group Sparassodonta, which were metatherians that inhabited South America during the Cenozoic. Unlike other remains assigned to the family Thylacosmilidae that had been found previously, Anachlysictis is the first record of such borhyaenoids in northern South America, and also most primitive and ancient in the family. This species was found in the Villavieja Formation in the area of La Venta in Colombia, a famous fossil deposit in the Middle Miocene, based on fragments that include a front portion of the lower jaw, with an incipient molar tooth and a piece of carnassial from the front of the maxilla.
Colombophis is an extinct genus of snakes of the clade Alethinophidia, a group of "primitive" snakes. The genus was first recognized in the Villavieja Formation in the town of Los Mangos, part of the known fossil fauna of La Venta in the department of Huila (Colombia), in the middle Miocene. With the remains of a fossil snake was erected the species Colombophis portai in 1977, based on forty fragmentary vertebrae. These vertebrae are characterized by a low neural spine, and subdivided paradiapophysis and thin zygosphen. The vertebrae are medium to large, so the snake would measure about 1.77 metres long, similar in size to the current Boa constrictor.
Proborhyaenidae is an extinct family of metatherian mammals of the order Sparassodonta, which lived in South America from the Eocene (Mustersan) until the Oligocene (Deseadan). Sometimes it has been included as a subfamily of their relatives, the borhyaenids. Body mass estimates suggest that proborhyaenids could weigh up to 150 kilograms (330 lb), making them some of the largest known metatherians. Proborhyaenid remains have been found in western Bolivia, Uruguay, southern Brazil, and the provinces of Mendoza, Salta, and Chubut, in Argentina.
Thylacosmilidae is an extinct family of metatherian predators, related to the modern marsupials, which lived in South America between the Miocene and Pliocene epochs. Like other South American mammalian predators that lived prior to the Great American Biotic Interchange, these animals belonged to the order Sparassodonta, which occupied the ecological niche of many eutherian mammals of the order Carnivora from other continents. The family's most notable feature are the elongated, laterally flattened fangs, which is a remarkable evolutionary convergence with other saber-toothed mammals like Barbourofelis and Smilodon.
Stagodontidae is an extinct family of carnivorous metatherian mammals that inhabited North America and Europe during the late Cretaceous, and possibly to the Eocene in South America.
Pharsophorus is an extinct genus of borhyaenoid sparassodont that inhabited South America during the Middle to Late Oligocene epoch.
Hondadelphys is an extinct genus of carnivorous sparassodonts, known from the Middle Miocene of Colombia. The type species, H. fieldsi, was described in 1976 from the fossil locality of La Venta, which hosts fossils from the Villavieja Formation. Hondadelphys was originally interpreted as belonging to the opossum family Didelphidae, but subsequently assigned to its own family, Hondadelphidae and interpreted as a basal sparassodont. The genus name refers to the Honda Group, the stratigraphic group in which the fossils of this animal were first found, combined with delphys (Greek for "womb", a common suffix used for opossum-like metatherians).
The "Gurlin Tsav" skull is a currently unnamed carnivorous metatherian fossil from the Nemegt Formation of Mongolia. Composed of a single semi-complete skull, this specimen is notable in regards to the evolution and systematics of Metatheria as a whole, and thus nigh-omnipresent in phylogenetic analyses of this group.
Anatoliadelphys maasae is an extinct genus of predatory metatherian mammal from the Eocene of Europe. It was an arboreal, cat-sized animal, with powerful crushing jaws similar to those of the modern Tasmanian devil. Although most mammalian predators of the northern hemisphere in this time period were placentals, Europe was an archipelago, and the island landmass now forming Turkey might have been devoid of competing mammalian predators, though this may not matter since other carnivorous metatherians are also known from the Cenozoic in the Northern Hemisphere. Nonetheless, it stands as a reminder that mammalian faunas in the Paleogene of the Northern Hemisphere were more complex than previously thought, and metatherians did not immediately lose their hold as major predators after their success in the Cretaceous.
Miocochilius is an extinct genus of small notoungulate mammals native to South America. The genus lived during the Middle Miocene epoch. The genus contains two described species, the type species M. anomopodus described in 1953 by Ruben Arthur Stirton and M. federicoi, described and included in the genus by Darin A. Croft.
