Question

Echidna is an oviparous animal, even then it is considered a mammal. Why?

Answer 1

Mammals are viviparous organisms while Echidna isoviparous, even then it is placed in class Mammalia asit possesses the basic mammalian characters like thepresence of mammary glands, diaphragm between thoraxand abdomen, four-chambered heart, non-nucleated RBCs,etc. However, due to its oviparous nature. Echidna hasnbeen assigned an infra class Prototheria-under the class mammalia.