Placental mammals are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguished from monotremes and marsupials in that the fetus is carried in the uterus of its mother to a relatively late stage of development. The name is something of a misnomer, considering that marsupials also nourish their fetuses via a placenta, though for a relatively briefer period, giving birth to less-developed young, which are then nurtured for a period inside the mother's pouch. Placentalia represents the only living group within Eutheria, which contains all mammals that are more closely related to placentals than they are to marsupials.
Eutheria, also called Pan-Placentalia, is the clade consisting of placentals and all therian mammals that are more closely related to placentals than to marsupials.
Creodonta is a former order of extinct carnivorous placental mammals that lived from the early Paleocene to the late Miocene epochs in North America, Europe, Asia and Africa. Originally thought to be a single group of animals ancestral to the modern Carnivora, this order is now usually considered a polyphyletic assemblage of two different groups, the oxyaenids and the hyaenodonts, not a natural group. Oxyaenids are first known from the Palaeocene of North America, while hyaenodonts hail from the Palaeocene of Africa.
Condylarthra is an informal group – previously considered an order – of extinct placental mammals, known primarily from the Paleocene and Eocene epochs. They are considered early, primitive ungulates and is now largely considered to be a wastebasket taxon, having served as a dumping ground for classifying ungulates which had not been clearly established as part of either Perissodactyla or Artiodactyla, being composed thus of several unrelated lineages.
Oxyaenidae is a family of extinct carnivorous placental mammals. Traditionally classified in order Creodonta, this group is now classified in its own order Oxyaenodonta within clade Pan-Carnivora in mirorder Ferae. The group contains four subfamilies comprising fourteen genera. Oxyaenids were the first to appear during the late Paleocene in North America, while smaller radiations of oxyaenids in Europe and Asia occurred during the Eocene.
Palaeoryctes is an extinct paraphyletic genus of mammals from paraphyletic subfamily Palaeoryctinae within family Palaeoryctidae, that lived in North America and Africa from middle Paleocene to early Eocene.
Protungulatum is an extinct genus of eutherian mammals within extinct family Protungulatidae, and is possibly one of the earliest known placental mammals in the fossil record, that lived in North America from the Late Cretaceous to early Paleocene.
Eurymylidae is a family of extinct simplicidentates. Most authorities consider them to be basal to all modern rodents and may have been the ancestral stock whence the most recent common ancestor of all modern rodents arose. However, the more completely known eurymylids, including Eurymylus, Heomys, Matutinia, and Rhombomylus, appear to represent a monophyletic side branch not directly ancestral to rodents. Huang et al. (2004) have argued that Hanomys, Matutinia, and Rhombomylus form a clade characterized by distinctive features of the skull and dentition that should be recognized as a separate family, Rhombomylidae. Eurymylids are only known from Asia.
Leptictida is a possibly paraphyletic extinct order of eutherian mammals. Their classification is contentious: according to cladistic studies, they may be (distantly) related to Euarchontoglires, although they are more recently regarded as the first branch to split from basal eutherians. One recent large-scale cladistic analysis of eutherian mammals favored lepictidans as close to the placental crown-clade; and several other recent analyses that included data from Cretaceous non-eutherian mammals found Leptictis to belong to the superorder Afrotheria.
Mixodectidae is an extinct family of insectivorous placental mammals in the order Dermoptera. The mixodectids originated in the late Cretaceous and survived into the Paleocene in Europe and North America.
Apatemyidae is an extinct family of placental mammals that took part in the first placental evolutionary radiation together with other early mammals, such as the leptictids. Their relationships to other mammal groups are controversial; a 2010 study found them to be basal members of Euarchontoglires.
The Willwood Formation is a sedimentary sequence deposited during the late Paleocene to early Eocene, or Clarkforkian, Wasatchian and Bridgerian in the NALMA classification.
The Conglomérat de Cernay is a geologic formation in Champagne-Ardenne, northern France. It preserves fossils dating back to the Thanetian stage of the Paleocene period. The lizard Cernaycerta and placental mammal Bustylus cernaysi are named after the formation.
Hyaenodonta is an extinct order of hypercarnivorous placental mammals of clade Pan-Carnivora from mirorder Ferae. Hyaenodonts were important mammalian predators that arose during the early Paleocene in Europe and persisted well into the late Miocene.
Machaeroidinae ("dagger-like") is an extinct subfamily of carnivorous saber-toothed placental mammals from extinct family Oxyaenidae, that lived from the early to middle Eocene of Asia and North America. Traditionally classified as hyaenodonts, this group is now classified as a member of the family Oxyaenidae.
Palaeanodonta is an extinct clade of stem-pangolins. They were insectivorous (myrmecophagous), possibly fossorial, and lived from the middle Paleocene to early Oligocene in North America, Europe and Asia. While the taxonomic grouping of Palaeanodonta has been debated, it is widely thought that they are a sister group to pangolins.
Zalambdalestidae is a clade of Asian eutherians occurring during the Cretaceous. Once classified as Glires, features like epipubic bones and various cranial elements have identified these animals as outside of Placentalia, representing thus a specialised clade of non-placental eutherians without any living descendants, and potentially rather different from modern placentals in at least reproductive anatomy.
Oxyaeninae is an extinct subfamily of placental mammals from extinct family Oxyaenidae, that lived in Asia, North America and Europe from the late Paleocene to middle Eocene.
Limnocyoninae is a subfamily of extinct predatory mammals from extinct order Hyaenodonta. Fossil remains of these mammals are known from late Paleocene to late Eocene deposits in North America and Asia. Limnocyonines had only two molars in the upper and lower dentition.
Metacheiromyidae is an extinct paraphyletic family of myrmecophagous placental mammals within extinct order Palaeanodonta, that lived in North America and Europe from the late Paleocene to middle Eocene.
