There are exceptions to every rule, some reptiles and fish bear live young, and some mammals lay eggs Monotremes (/ ˈmɒnətriːmz /) are mammals of the order monotremata They are the only group of living mammals that lay eggs, rather than bearing live young The extant monotreme species are the platypus and the four species of echidnas Monotremes are typified by structural differences in their brains, jaws, digestive tracts, reproductive tracts, and other body parts, compared to the more. Why do some mammals lay eggs instead of giving birth
Some mammals, like monotremes, reproduce by laying eggs instead of giving birth because they represent an ancient evolutionary stage between reptiles and modern mammals Millions of years ago, the ancestors of all mammals likely laid eggs, just like reptiles and birds do today While most mammals eventually adapted to give birth to live. With their ancient origins, strange biology, and limited range, platypuses and echidnas are natural marvels. Monotremes are the only type of mammal which can lay eggs There are five separate species of egg laying mammal, four species of echidna and the platypus
