monotreme, egg-laying mammal

the most primitive mammals comprising the only extant members of the subclass Prototheria

• echidna, spiny anteater, anteater — burrowing spine-covered monotreme of Australia having a long snout and claws for hunting ants and termites
• echidna, spiny anteater, anteater — New Guinea echidnas
• platypus, duckbill, duckbilled platypus, duck-billed platypus, Ornithorhynchus anatinus — small densely furred aquatic monotreme of Australia and Tasmania having a broad bill and tail and webbed feet; only species in the family Ornithorhynchidae

• prototherian — primitive oviparous mammals found only in Australia Tasmania and New Guinea