Definition of Prototheria in English:


plural noun

  • A group of mammals that comprises the monotremes and their extinct relatives.

    Subclass Prototheria, class Mammalia

    Compare with Theria
    • ‘They are often placed in a separate subclass from other mammals, Prototheria.’
    • ‘Triconodonta were viewed as broadly ancestral to the extinct Docodonta and to living monotremes, collectively grouped (often with Multituberculata) as Prototheria.’
    • ‘Later cladistic studies, beginning with that of Kemp, called into question the integrity of a broadly conceived ‘Prototheria.’’
    • ‘As noted, recognition of skull resemblances to monotremes and triconodonts led to later referral to ‘Prototheria,’ within a monophyletic Mammalia.’


Modern Latin (plural), from proto- ‘first, original’ + Greek thēr ‘wild beast’.