• Mammal (animal) tại Encyclopædia Britannica (tiếng Anh)
• BBC Wildlife Finder - video clips from the BBC's natural history archive
• GlobalTwitcher.com – All species in the world with distribution maps and images
• Paleocene Mammals, a site covering the rise of the mammals, paleocene-mammals.de
• Evolution of Mammals, a brief introduction to early mammals, enchantedlearning.com
• Tree of Life poster – Shows mammals' evolutionary relation to other organisms, tellapallet.com
• The Evolution of Mesozoic Mammals, a Rough Sketch, an informal introduction, home.arcor.de
• Carnegie Museum of Natural History, some discoveries of early mammal fossils, carnegiemnh.org
• High-Resolution Images of various Mammalian Brains, brainmaps.org
• Mammal Species, collection of information sheets about various mammal species, learnanimals.com
• Summary of molecular support for Epitheria, biology.plosjournals.org
• Mikko's Phylogeny Archive, fmnh.helsinki.fi
• European Mammal Atlas EMMA from Societas Europaea Mammalogica, european-mammals.org
• Marine Mammals of the World—An overview of all marine mammals, including descriptions, multimedia and a key, eti.uva.nl
• Mammalogy.org The American Society of Mammalogists was established in 1919 for the purpose of promoting the study of mammals, and this website includes a mammal image library

(tiếng Việt)

• Thú tại Từ điển bách khoa Việt Nam
• 174 loài Thú ở Việt Nam trên trang SVRVN