Which feature distinguishes monotremes from other mammals?
Monotremes, like platypus, are oviparous, laying eggs, unlike most mammals which are viviparous or ovoviviparous (NCERT, Chapter 4, page 59). All mammals have hair and four-chambered hearts.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Vertebrata - Aves and Mammalia
