monotreme /ˈmɒnəʊˌtriːm/

• 1.  

  N（名词） any mammal of the primitive order Monotremata, of Australia and New Guinea: egg-laying toothless animals with a single opening (cloaca) for the passage of eggs or sperm, faeces, and urine. The group contains only the echidnas and the platypus (澳大利亚和新几内亚)单孔目哺乳动物