Simplicidentata is a group of mammals that includes the rodents and their closest extinct relatives. The term has historically been used as an alternative to Rodentia, contrasting the rodents with their close relatives the lagomorphs. However, Simplicidentata is now defined as including all members of Glires that share a more recent common ancestor with living rodents than with living lagomorphs. Thus, Simplicidentata is a total group that is more inclusive than Rodentia, a crown group that includes all living rodents, their last common ancestor, and all its descendants. Under this definition, the loss of the second pair of upper incisors is a synapomorphic feature of Simplicidentata. The loss of the second upper premolar (P2) has also been considered as synapomorphic for Simplicidentata, but the primitive simplicidentate Sinomylus does have a P2.
Barylambda is an extinct genus of pantodont mammal from the middle to late Paleocene, well known from several finds in the Wasatchian DeBeque Formation of Colorado and the Clarkforkian Wasatch Formation to Tiffanian Fort Union Formation in Wyoming. Three species of Barylambda are currently recognized. The creature likely lived a life similar to that of a modern tapir, browsing on foliage and soft vegetation. Barylambda seems to have been quite successful for an early pantodont, though eventually it seems to have been replaced in its ecosystem by other pantodonts, such as Coryphodon.
Eomyidae is a family of extinct rodents from North America and Eurasia related to modern day pocket gophers and kangaroo rats. They are known from the Middle Eocene to the Late Miocene in North America and from the Late Eocene to the Pleistocene in Eurasia. Eomyids were generally small, but occasionally large, and tended to be squirrel-like in form and habits. The family includes the earliest known gliding rodent, Eomys quercyi.
Miacoidea is a former paraphyletic superfamily of extinct placental mammals that lived during the Paleocene and Eocene epochs, about 66-33,9 million years ago. This group had been traditionally divided into two families of primitive carnivorous mammals: Miacidae and Viverravidae. These mammals were basal to order Carnivora, the crown-group within the Carnivoramorpha.
Vulpavus is an extinct paraphyletic genus of placental mammals from clade Carnivoraformes, that lived in North America from the early to middle Eocene.
Miocyon is an extinct genus of placental mammals from clade Carnivoraformes, that lived in North America from the early to late Eocene.
Oodectes is an extinct paraphyletic genus of placental mammals from clade Carnivoraformes, that lived in North America from the early to middle Eocene.
Palaearctonyx is an extinct genus of omnivorous placental mammals from clade Carnivoraformes, that lived in North America from the early to middle Eocene.
Prodaphaenus is an extinct genus of placental mammals from clade Carnivoraformes, that lived in North America during the middle Eocene.
Tapocyon is an extinct genus of placental mammals from clade Carnivoraformes, that lived in North America during the middle Eocene. Tapocyon was about the size of a coyote and is believed to have been a good climber that spent a lot of time in trees.
Uintacyon is an extinct paraphyletic genus of placental mammals from clade Carnivoraformes, that lived in North America from the early to middle Eocene.
Bryanictis is an extinct genus of placental mammals from extinct subfamily Didymictinae within extinct family Viverravidae, that lived in North America, from the early to late Paleocene.
Intyrictis is an extinct genus of placental mammals from extinct subfamily Didymictinae within extinct family Viverravidae, that lived in North America during the early Paleocene.
Pristinictis is an extinct genus of placental mammals from extinct subfamily Didymictinae within extinct family Viverravidae, that lived in North America during middle Paleocene.
Procynodictis is an extinct genus of placental mammals from clade Carnivoraformes, that lived in North America from the early to middle Eocene.
Raphictis is an extinct genus of placental mammals from extinct subfamily Didymictinae within extinct family Viverravidae, that lived in North America during late Paleocene.
Thalassictis is an extinct genus of terrestrial carnivore in the family Hyaenidae that lived in Asia during the Middle to Late Miocene and in Europe and North Africa during the Late Miocene.
Lagurus is a genus in the subfamily Arvicolinae. Lagurus includes a single living species, the steppe lemming of central Eurasia. The North American sagebrush vole has also been included in Lagurus, but is likely not closely related. The earliest fossils of Lagurus, allocated to Lagurus arankae, appear in the Late Pliocene. Two other fossil species, Lagurus pannonicus and Lagurus transiens, are thought to be part of a lineage that led to the living steppe lemming.
Viverravus is an extinct genus of placental mammals from extinct subfamily Viverravinae within extinct family Viverravidae, that lived in North America, Europe and Asia from the middle Paleocene to middle Eocene.
Hemipsalodon is an extinct genus of hyainailourid hyaenodonts from the subfamily Hyainailourinae that lived in North America during the middle to late Eocene.
