Introduction to Monotremata

Ornithorhynchus anatinus

The order Monotremata is a fairly ancient mammalian taxon.  It includes two families, Ornithorhynchidae (Ornithorhynchus*) and Tachyglossidae (the echidnas, Tachyglossusand Zaglossus).   Although considered mammals, monotremes have several characteristics not generally considered mammalian.  Among these are oviparity, a cloaca (hence the name monotreme, Greek for "one hole"), lack of functional teeth, the presence of poison glands (Walker 1964), and milk secretion in a "mammary patch" rather than through teats.  Like marsupials, they have anterior testes and a forked penis (Anderson and Jones 1967).   Their range is limited to Australia, Tasmania, and New Guinea (Walker 1964).

*Don "The Mango King," Yungaburra, Queensland fruit stand proprietor and self-proclaimed platypus expert, disputes this account of platypus phylogeny.  He places the platypus in Anatidae, the duck family (personal communication, 11/98).

 Tachyglossus sp.


A young Tachyglossus
  • Specialized for digging to find food and escape predation
  • Have poor vision but excellent smell and hearing
  • Lack teeth, but use a long (15-18 cm) tongue to feed on ants and termites
  • Females develop and use a pouch (marsupium) during the breeding season
  • Humans appear to be only natural enemy -- can live up to 50 years in captivity
  • Genus Tachyglossus, the short-beaked echidna, occurs throughout Australia and Tasmania
  • Genus Zaglossus, the long-beaked echidna, occurs only in New Guinea
    Source: Anderson and Jones, 1967

All images courtesy unless otherwise noted.
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This page is a class assignment for Animal Physiology at Davidson College.  For questions or comments, please email Will White.