A monotreme is a type of mammal known for their primitive trait of laying eggs instead of giving live birth as marsupials and placentals do. They suckle their young like all mammals, but they also lack breasts, instead secreting milk from certain locations on the mother's body.

There are five monotreme species still alive today. One is the platypus, native to Australia, while the other four are echidnas, which inhabit the island of New Guinea (and also Australia in the case of the short-beaked echidna).

See also:

• mammal
• monotreme
• echidna
• platypus

Other rankings

• tag group:species
• mammal
• afrosoricid - Golden mole and tenrec.
• bovine - Buffalo, cattle, yak, etc.
• camelid - Alpaca, camel, llama, etc.
• canine - Dog, fox, wolf, etc.
• caprine - Goat, ibex, sheep, etc.
• cervine - Elk, moose, reindeer, etc.
• cetacean - Dolphin, porpoise, whale, etc.
• equine - Donkey, horse, zebra, etc.
• eulipotyphlan - Hedgehog, mole, shrew, etc.
• euplerid - Fanaloka, fossa, vontsira, etc.
• feline - Cat, lion, tiger, etc.
• giraffid - Giraffe, okapi, etc.
• herpestid - Mongoose
• lagomorph - Rabbit, hare, pika, etc.
• marsupial - Kangaroo, koala, opossum, etc.
• mephitid - Skunks and stink badgers.
• monotreme - Echidna and platypus
• mustelid - Ferret, otter, weasel, etc.
• pinniped - Sea lion, seal, walrus, etc.
• porcine - Boar, pig, warthog, etc.
• primate - Ape, lemur, monkey, etc. (excludes human)
• proboscidean - Elephant, mammoth, mastodon, etc.
• procyonid - Kinkajou, raccoon, ring-tailed cat, etc.
• rodent - Mouse, rat, squirrel, etc.
• ursine - Grizzly bear, panda, polar bear, etc.
• viverrid - Civet, genet, linsang, etc.
• xenarthran - Anteater, armadillo, and sloth.