The Classification of Nontherian Mammals

On the basis of a unique specialization of the braincase the four nontherian orders of mammals—the living Monotremata and the extinct Tricono-donta, Docodonta, and Multituberculata—are united into a single subclass, Prototheria. The Triconodonta and Docodonta are closely related and are grouped together in the infraclass Eotheria. The Monotremata and Multituberculata are only remotely allied to all other mammals and are each placed in a separate infraclass—Ornithodelphia for the monotremes and Allotheria for the Multituberculates. A classification of prototherian mammals to family is presented.