| Xenocynus Temporal range: | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Clade: | Metatheria |
| Genus: | † Xenocynus |
| Species: | †X. crypticus |
| Binomial name | |
| †Xenocynus crypticus Carneiro et. al., 2024 | |
Xenocynus is an extinct genus of metatherian mammal that lived in Brazil during the Eocene. It contains a single species, Xenocynus crypticus. [1]
Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals. First proposed by Thomas Henry Huxley in 1880, it is a more inclusive group than the marsupials; it contains all marsupials as well as many extinct non-marsupial relatives. It is one of two groups placed in the clade Theria alongside Eutheria, which contains the placentals. Remains of metatherians have been found on all of Earths continents.
Podocnemididae is a family of pleurodire (side-necked) turtles, once widely distributed. Most of its 41 genera and 57 species are now extinct. Seven of its eight surviving species are native to South America: the genus Peltocephalus, with two species, only one of which is extant ; and the genus Podocnemis, with six living species of South American side-necked river turtles and four extinct. There is also one genus native to Madagascar: Erymnochelys, the Madagascan big-headed turtle, whose single species E. madagascariensis.
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.
Herpetotherium is an extinct genus of metatherian mammal, belonging to the possibly paraphyletic family Herpetotheriidae. Native to North America from the Eocene to Early Miocene, fossils have been found in California, Oregon, Texas, Florida, Montana, Wyoming, Colorado, North and South Dakota, Nebraska, and Saskatchewan. The oldest species, H. knighti, is dated to around 50.3 mya, and the most recent, an unnamed species, may be as recent as 15.97 mya. A morphological analysis of marsupials and basal metatherians conducted in 2007 found Herpetotherium to be the sister group to extant marsupials. It is the youngest known metatherian from North America until the migration of the Virginia opossum from South America within the last 2 million years.
Herpetotheriidae is an extinct family of metatherians, closely related to marsupials. Species of this family are generally reconstructed as terrestrial, and are considered morphologically similar to modern opossums. They are suggested to have been insectivores. Fossils of herpetotheriids come from North America, Asia, Europe, Africa, and perhaps South America. The oldest representative is Maastrichtidelphys from the latest Cretaceous (Maastrichtian) of the Netherlands and the youngest member is Amphiperatherium from the Middle Miocene of Europe. The group has been suggested to be paraphyletic, with an analysis of petrosal anatomy finding that North American Herpetotherium was more closely related to marsupials than the European Peratherium and Amphiperatherium.
Peratherium is a genus of metatherian mammals in the family Herpetotheriidae that lived in Europe and Africa from the Early Eocene to the Early Miocene. Species include the following:
Chulpasia is an extinct genus of Eocene marsupial related to today's shrew opossums. It was a small animal, about 20 centimetres (7.9 in) long, with an omnivorous diet. Its diet probably included seeds, small fruits, and insects. Fossils were found in the Muñani Formation in present-day Peru.
Mimoperadectes is an extinct genus of metatherian mammal from the Eocene of North America.
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. The largest species, Proborhyaena gigantea, is estimated to be about the size of a spectacled bear, with its skull reaching 60 cm (2.0 ft) in length, and body mass estimates up to approximately 90–200 kg (200–440 lb), making the proborhyaenids 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.
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.
Polydolopimorphia is an extinct order of metatherians, closely related to extant marsupials. Known from the Paleocene-Pliocene of South America and the Eocene of Antarctica, they were a diverse group during the Paleogene, filling many niches, before declining and becoming extinct at the end of the Neogene. It is divided into two suborders, Bonapartheriiformes, and Polydolopiformes Most members are only known from jaw fragments, which have their characteristically generally bunodont teeth. The morphology of their teeth has led to proposals that polydolopimorphians may be crown group marsupials, nested within Australidelphia, though this proposal, has been questioned, with other analyses finding them outside of crown-group Marsupialia. The monophyly of the group has been questioned, due to the possibility of the characteristic bunodont teeth emerging convergently in unrelated groups, rather than reflecting a true phylogenetic relationship. The group contained omnivorous, frugivorous and herbivorous forms.
Anatoliadelphys maasae is an extinct genus of predatory metatherian mammal from the Eocene of Anatolia. 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.
Antarctodolops is an extinct genus of polydolopimorphian metatherian similar to, but not closely related to, the living shrew opossums. It lived on Seymour Island, Antarctica in the Eocene. Two species, Antarctodolops dailyi and Antarctodolops mesetaense, have been found. These species were different sizes, with A. mesetaense being the larger.
The Itaboraí Formation is a highly fossiliferous geologic formation and Lagerstätte of the Itaboraí Basin in Rio de Janeiro, southeastern Brazil. The formation reaching a thickness of 100 metres (330 ft) is the defining unit for the Itaboraian South American land mammal age (SALMA), dating to the Early Eocene, approximately 53 to 50 Ma.
Anatoliadelphyidae is an extinct family of metatherian mammals, endemic to the Pontide terrane, during the Middle Eocene (Lutetian), around 43 million years ago, when the terrane formed an island landmass with an insular endemic fauna, which also included herpetotheriid and polydolopimorphian metatherians, as well as archaic pleuraspidotheriid ungulates and enigmatic insectivores. The cat-sized Anatoliadelphys is the best known member, and is thought to have been a carnivore or omnivore.
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.
Asmithwoodwardia is an extinct genus of mammals, from the order Litopterna. It lived during the Late Paleocene and the Early Eocene, and its fossilized remains were found in South America.
Protolipterna is an extinct genus of mammal, belonging to the order Litopterna. It lived during the Late Paleocene and the Early Eocene, in what is now South America.
Amphiperatherium is an extinct genus of metatherian mammal, closely related to marsupials. It ranged from the Early Eocene to the Middle Miocene in Europe. It is the most recent metatherian known from the continent.
Indodelphis is an extinct genus of opossum-like metatherian from Eocene of Cambay Shale Formation of India. The type and the only species is Indodelphis luoi.