What Are The 3 Monotremes?

What Are The 3 Monotremes? The echidna and the duck-billed platypus, which are the only egg-laying mammals, are so distinct that they are assigned to a discrete subclass, the Prototheria, which includes the order Monotremata, separate from the more familiar and well-studied placental mammals. Which of the following is a monotreme quizlet? Monotremes or egg-laying