How many groups of mammals are there there are 4 groups? - Answers

There are four main groups of mammals: monotremes, marsupials, placental mammals, and the recently recognized group of egg-laying mammals. Monotremes, like the platypus, lay eggs, while marsupials, such as kangaroos, give birth to underdeveloped young that typically continue developing in a pouch. Placental mammals, which include humans and most other mammals, carry their young in the womb until they are more fully developed. Each group exhibits unique reproductive and developmental traits.