MICROANATOMY

Detailed explanation-1: -Monotremes are mammals that can lay eggs (oviparous), this is the primary difference between monotremes and other mammals. They are the more primitive animals of all the other mammalian orders (marsupials and placental). Therefore, they have much simpler body structures such as a primitive skeletal system.

Detailed explanation-2: -Why then are they considered mammals you may be wondering? Like other mammals, monotremes are warm-blooded. They have hair on their bodies and produce milk to feed their young. In echidnas, the female lays eggs into a pouch of skin on her stomach, where she carries them until they hatch.

Detailed explanation-3: -Their genomes are similar in size to those of placentals, but their chromosomes are quite distinctive. Marsupials have a few very large and very conserved chromosomes, while monotremes show a reptile-like size dichotomy and have a unique chain of ten sex chromosomes.

Detailed explanation-4: -Eggs and Lactation However, unlike reptiles, female monotremes retain their eggs for some time (typically for two or three weeks) and actively provide the eggs with nutrients. Female platypuses lay their eggs in burrows. Echidna females have a pouch in which they store their eggs and later nurse their young.