- monotreme
[monotreme 词源字典]
- "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", Mid 19th century: from mono- 'single' + Greek trēma 'hole'.[monotreme etymology, monotreme origin, 英语词源]