Monotremes

Egg-laying Mammals

Echidna. Photo by Dr. Lloyd Glenn Ingles © 2001 California Academy of Sciences.   There are only five living monotreme species: the duck-billed platypus and four species of echidna (also known as spiny anteaters). All of them are found only in Australia and New Guinea. Monotremes are not a very diverse group today, and there has not been much fossil information known until rather recently. In some ways, monotremes are very primitive for mammals because, like reptiles and birds, they lay eggs rather than having live birth. In a number of other respects, monotremes are rather derived, having highly modified snouts or beaks, and modern adult monotremes have no teeth. Like other mammals, however, monotremes have a single bone in their lower jaw, three middle ear bones, high metabolic rates, hair, and they produce milk to nourish the young. Monotremes are one of the three main groups of living mammals, along with placentals and marsupials. The monotremes are typified by structural differences in their brains, jaws, digestive tract, reproductive tract, and other body parts compared to the more common mammalian types.  Order: Monotremata Scientific name: Monotremata Class: Mammalia Phylum: Chordata Kingdom: Animalia MONOTREME Gestation period Platypus: 10 – 14 days Short-beaked echidna: 18 days Western long-beaked echidna: 10 days