The Cenozoic is Earth's current geological era, representing the last 66 million years of Earth's history. It is characterized by the dominance of mammals, birds, conifers, and angiosperms. It is the latest of three geological eras of the Phanerozoic Eon, preceded by the Mesozoic and Paleozoic. The Cenozoic started with the Cretaceous–Paleogene extinction event, when many species, including the non-avian dinosaurs, became extinct in an event attributed by most experts to the impact of a large asteroid or other celestial body, the Chicxulub impactor.
Opossums are members of the marsupial order Didelphimorphia endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 126 species in 18 genera. Opossums originated in South America and entered North America in the Great American Interchange following the connection of North and South America.
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.
Paucituberculata is an order of South American marsupials. Although currently represented only by the seven living species of shrew opossums, this order was formerly much more diverse, with more than 60 extinct species named from the fossil record, particularly from the late Oligocene to early Miocene epochs. The earliest paucituberculatans date to the late Paleocene. The group went through a pronounced decline in the middle Miocene epoch, which resulted in the extinction of all families of this order except for the living shrew opossums (Caenolestidae). Extinct families of Paucituberculatans include Pichipilidae, Palaeothentidae, and Abderitidae.
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.
The Itaboraian age is a period within the Early Eocene geologic time epoch of the Paleogene, used more specifically with South American land mammal ages (SALMA). It follows the Riochican and precedes the Casamayoran age.
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.
Pterodon is an extinct genus of hyaenodont in the family Hyainailouridae, containing five species. The type species Pterodon dasyuroides is known exclusively from the late Eocene to the earliest Oligocene of western Europe. The genus was first erected by the French zoologist Henri Marie Ducrotay de Blainville in 1839, who said that Georges Cuvier presented one of its fossils to a conference in 1828 but died before he could make a formal description of it. It was the second hyaenodont genus with taxonomic validity after Hyaenodon, but this resulted in taxonomic confusion over the validities of the two genera by other taxonomists. Although the taxonomic status of Pterodon was revised during the late 19th and early 20th centuries, it became a wastebasket taxon for other hyaenodont species found in Africa and Asia. Today, only the type species is recognized as belonging to the genus while four others are pending reassessment to other genera.
The Santa Rosa local fauna consists of the animals found in the Paleogene fossil site of Santa Rosa in eastern Peru. The age of the Santa Rosa fauna is difficult to determine, but may be Eocene (Mustersan) or Oligocene (Deseadan).
This paleomammalogy list records new fossil mammal taxa that were described during the year 2012, as well as notes other significant paleomammalogy discoveries and events which occurred during that year.
Siamoperadectes is a genus of non-marsupial metatherian from the Miocene of Thailand. A member of Peradectidae, it is the first member of its clade known from South Asia, and among the last non-marsupial metatherians.
Groeberiidae is a family of strange non-placental mammals from the Eocene and Oligocene epochs of Patagonia, Argentina and Chile, South America. Originally classified as paucituberculate marsupials, they were suggested to be late representatives of the allothere clade Gondwanatheria. However, the relationship of the type genus, Groeberia, to Gondwanatheria has been firmly rejected by other scholars.
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.
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.
Hondonadia is an extinct genus of Late Eocene to Early Oligocene (Tinguirirican) marsupials related to today's shrew opossums and with similar features as the related Rosendolops. The type species Hondonadia feruglioi was described by Goin and Candela in 1998. In later years, five more species were recognized, of which Pascualdelphys fierroensis, described by Flynn and Wyss in 1999, that was in 2010 synonymized with Hondonadia.
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.
Peradectidae is a family of small metatherian mammals, spanning from the Paleocene to the Miocene. Fossils are known from the Northern Hemisphere, including Europe, Asia and North America. The monophyly of the group has been questioned, with some authors suggesting that Peradectes should be the only genus placed in the family. The morphology of peradectids has been considered to be similar to opossums, with at least some exhibiting morphology suggesting a tree dwelling arboreal/scansorial lifestyle. Their diet is suggested to have included insects and fruit.
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.
