What is common between parrot, platypus and kangaroo?

Only birds and mammals are homoiotherms. Parrot and platypus have toothless jaws and show oviparity. Kangaroo show viviparity. Platypus and kangaroo have functional post anal tail. Related Theory The platypus (Ornithorhynchus anatinus), sometimes referred to as the duck-billed platypus, is a semiaquatic, egg-laying mammal endemic to eastern Australia. It is a monotreme, and shows oviparity (exception to mammals).