Artiodactyla
Antilocapridae, Bovidae, Camelidae, Cervidae, Giraffidae, Hippopotamidae, Suidae, Tayassuidae, Tragulidae, Artiodactyls and other ruminants, British and European Ungulates, Ultimate Ungulate Page: Artiodactyla
Carnivora
Canidae, Felidae, Herpestidae, Hyaenidae, Mephitidae, Mustelidae, Procyonidae, Ursidae, Viverridae, Carnivore Conservation Online, Lioncrusher's Domain, Order Carnivora, Small Carnivore Taxon Advisory Group
Cetacea
Baleen Whales, Toothed Whales, Cetacea, Cetacea: Whales, Dolphins, and Porpoises, Cetacean Encyclopaedia, Cetaceans: The Whales and Dolphins, Cetonaut, Classification of Whales, Deafwhale Society, Dolphin Dreams UK, Dolphin Institute, Dolphins and Whales in Greece
Chiroptera
Pteropodidae, Rhinolophidae, Vespertilionidae, Australasian Bat Society, Bat Atlas, Bat Call Library, Bat Planet - Bourges Museum, Bat Thematic Unit, Batcall Directory, Bats in Australia, Brain Museum - Chiroptera, British Bats, Chiroptera - Bats
Elephants
African Elephants, Asian Elephant, Absolut Elephant, African and Asian Elephants, Elephant Anatomy, Elephant Country, Elephant News, Elephant project - Elefriends, Elephants at Nature Haven, Elephants in Zoo and Circus, European Elephant Keeper and Managers Association, Introduction to the Proboscidea
Insectivora
Golden Moles, Hedgehogs, Moles and Desmans, Shrews, Solenodons, Tenrecs, Order Insectivora
Marsupials
American Opossums, Kangaroos, Koalas, Thylacine, Wallabies, Animalinfo.org - Kangaroo, Wallaby, Carnivores, Australian Department of the Environment - Biodive, Bandicoots at the Beach, Bilby - Greater Bilby, Bilby Appreciation Society, Mahogany glider - the one that nearly got away!, Marsupial Mammals - University of California, Berk, Marsupial webring, Marsupials of Argentina, Marsupials of Australia, Carnivorous Marsupials
Perissodactyla
Equidae, Rhinocerotidae, Tapiridae, Animals with Odd-Numbered Hooves, Ultimate Ungulate Page: Perissodactyla
Pinnipedia
Walrus, Elephant Seal RadioCam, Evolution, Classification, and Distribution of Pin, Friends of the Elephant Seal, Marine Mammal Research Consortium - Steller Sea Li, Mom - Association for the Study and Protection of , Monachus.org, Northern Elephant Seal Experience, Online Zoologists: Pinnipeds, Pagophilus.org, Pictures: Seals and Sea Lions
Primates
Bushbabies, Callithricidae, Cebidae, Cercopithecidae, Hominidae, Hylobatidae, Indriidae, Lemuridae, Grungy Ape, Ink., International Primate Protection League, Jonathan's Awesome Page of Monkeys, Order Primates, Primata, Primate Fact Sheet Links, Primates, Primates, Primates.com, The Primates
Rodents
Castoridae, Hydrochoeridae, Muridae, Sciuridae, Order Rodentia, Rodentia, Rodentia, The Rodents
Sirenia
Dugong, Manatees, SireNews, Sirenia: Manatees, Dugong, and Sea Cow, Sirenian International, SirenianVoice
Tubulidentata
Aangelina Aardvark, Aardvark, Aardvark (Earth pig, Ant bear), Aardvark (Orycteropus afer) skeleton, Aardvark - Wikipedia, Aardvarkland - All About Aardvarks, Aardvarks: Centre Burrow, AWF Wildlives: Aardvark, BBC Online - Really Wild Zone - Aardvark, Enchanted Learning - Aall Aabout Aardvarks
Xenarthra
Anteaters, Armadillos, Sloths, Order Xenarthra, Order Xenarthra, Order Xenarthra, Xenarthra.org
Animal Info - Rare, Threatened and Endangered Mamm
Biology, ecology, habitat, and status of rare, threatened and endangered species of mammals and information on their native countries: biodiversity, ecosystems, population, and land use.
Australian Mammals: Living and Extinct
Species profiles including habitats, characteristics, behavior, breeding cycles, feeding, images, and range maps.
Class Mammalia
Introduction to mammals, with detailed information about subclasses and orders of mammals, from the Animal Diversity Web.
European Mammal Database by Teddy Wilkin
A database of historic trends of mammals populations in Europe; an undergraduate project with references.
Mammal Species of the World
Names and literature citations for the 4,629 currently recognized species of mammals, in a taxonomic hierarchy that includes Order, Family, Subfamily, and Genus.
Mammals of Texas
Guide to the 181 species of Texas mammals, based on Davis and Schmidly's classic printed handbook.
MAMMFAUN
A bibliography of publications concerning the geographical distribution of mammals.
Mark Kostich - Rare and Endangered Mammals
High quality images of species from around the world. Includes Giant Muntjac, Owston's Civet, Binturong, Spotted Linsang, Pangolin, Yellow Throated Marten, Indian Civet, Genet Cat, Sun Bear, Pygmy Loris, and Slow Loris.
National Museum of Natural History Division of Mam
With roughly 570,000 voucher specimens, by far the world's largest mammal collection. Located in Washington, DC, USA.
Tasmanian Mammal List
Guide to Tasmania's mammals.
Terrestrial Mammals of the Arctic
Checklist of the 48 species.
The Ultimate Ungulate Page
Biology of the infraorder Ungulata and related groups, including Artiodactyla, aardvarks, elephants, hyraxes, sea cows, and Perissodactyla.
UCMP Hall of Mammals
University of California Museum of Paleontology site providing an introduction the Class Mammalia and to the subcategories of mammals, including the marsupials, monotremes, multituberculata, and the eutheria (placentals).
University of Kansas Natural History Museum: Divis
The mammal collection is one of the largest in North America and the second largest university collection, with over 158,000 cataloged specimens.
Walker's Mammals of the World
Online version of the reference work by Ronald W. Nowak. Some sections are free, but subscription is required for most areas.