monotreme
/ˈmɒnəʊtriːm/noun
1- Zoology a primitive mammal that lays large yolky eggs and has a common opening for the urogenital and digestive systems. Monotremes are now restricted to Australia and New Guinea, and comprise the platypus and the echidnas.【动】单孔目动物。
1.1
- Order Monotremata and subclass Prototheria: two families.单孔目, 原兽亚纲：2科。
词源
mid 19th cent.: from MONO- 'single' + Greek trēma 'hole'.