About 490 species of mammals are recorded in the United States. Unincorporated territories such as Puerto Rico, Guam or Northern Mariana Islands are not covered. Mammals introduced and extinct in the Holocene except Pleistocene/Holocene boundary are included. According to the IUCN Red List 3 of these species are critically endangered, 20 endangered, 15 vulnerable, 20 near threatened and 4 extinct. Some species are identified as indicated below: The following tags are used to highlight each species' conservation status as assessed by the International Union for Conservation of Nature: (v. 2013.2, the data is current as of March 5, 2014 ) and the Endangered Species Act: (the data is current as of March 28, 2014 )

Subclass: Theria

Infraclass: Metatheria

Order: Didelphimorphia (common opossums)

Didelphimorphia is the order of common opossums of the Western Hemisphere. Opossums probably diverged from the basic South American marsupials in the late Cretaceous or early Paleocene. They are small to medium-sized marsupials, about the size of a large house cat, with a long snout and prehensile tail.

Infraclass: Eutheria

Order: Cingulata (armadillos)

The armadillos are small mammals with a bony armored shell. They are native to the Americas. There are around 20 extant species. Only the nine-banded armadillo is found in the United States.

Order: Rodentia (rodents)

Rodents make up the largest order of mammals, with over 40% of mammalian species. They have two incisors in the upper and lower jaw which grow continually and must be kept short by gnawing. Most rodents are small though the capybara can weigh up to 45 kg. (Carolina northern flying squirrel G. s. coloratus, Virginia northern flying squirrel G. s. fuscus: ) (Delmarva fox squirrel, S. n. cinereus: ) (Mount Graham red squirrel, T. f. grahamensis: ) (Morro Bay kangaroo rat, D. h. morroensis: ) (Pacific pocket mouse, P. l. pacificus: ) (Preble's meadow jumping mouse, Z. h. preblei: ) (M. m. hualpaiensis: )

Order: Lagomorpha (lagomorphs)

The lagomorphs comprise two families, Leporidae (hares and rabbits), and Ochotonidae (pikas). Though they can resemble rodents, and were classified as a superfamily in that order until the early 20th century, they have since been considered a separate order. They differ from rodents in a number of physical characteristics, such as having four incisors in the upper jaw rather than two.

Order: Eulipotyphla (shrews, hedgehogs, moles, and solenodons)

Eulipotyphlans are insectivorous mammals. Shrews and solenodons closely resemble mice, hedgehogs carry spines, while moles are stout-bodied burrowers.

Order: Chiroptera (bats)

The bats' most distinguishing feature is that their forelimbs are developed as wings, making them the only mammals capable of flight. Bat species account for about 20% of all mammals. (P. t. virginianus:, P. t. ingens: )

Order: Carnivora (carnivorans)

There are over 260 species of carnivorans, the majority of which feed primarily on meat. They have a characteristic skull shape and dentition. (U. l. littoralis:, U. l. catalinae: , U. l. santarosae: , U. l. santacruzae: ) (Louisiana black bear, U. a. luteolus: ) (Grizzly bear, Ursus arctos horribilis:, California grizzly bear, Ursus arctos californicus: )

Order: Artiodactyla (even-toed ungulates)

The even-toed ungulates are ungulates whose weight is borne about equally by the third and fourth toes, rather than mostly or entirely by the third as in perissodactyls. There are about 220 artiodactyl species, including many that are of great economic importance to humans.

Order: Sirenia (manatees and dugongs)

Sirenia is an order of fully aquatic, herbivorous mammals that inhabit rivers, estuaries, coastal marine waters, swamps, and marine wetlands.

Order: Cetacea (whales)

The order Cetacea includes whales, dolphins and porpoises. They are the mammals most fully adapted to aquatic life with a spindle-shaped nearly hairless body, protected by a thick layer of blubber, and forelimbs and tail modified to provide propulsion underwater. (Northeast Pacific subpopulation: )

Introduced species