Monotremes (the platypus and echidnas) are highly specialized egg‐laying mammals found today only in Australia and New Guinea.

Keywords: monotremata; platypus; echidna; Australia; New Guinea

Figure 1.

Skeleton of the short‐beaked echidna, T. aculeatus. The posttemporal canal (ptc); cervical ribs (cr); epipubic bones (eb) (a feature shared with marsupials); and archaic shoulder girdle are considered to be primitive characteristics retained by monotremes, while ossified sternal ribs (sr) occur in birds but not most mammals. The solid build of the skeleton is attributed to the echidna's fossorial lifestyle. Courtesy of Anne Musser.

Figure 2.

The platypus, Ornithorhynchus anatinus. The platypus (Ornithorhynchus anatinus) is beautifully adapted to its aquatic lifestyle, with a thick, waterproof pelt; dorsally placed eyes; streamlined body and extensively webbed forefeet. Its extraordinarily sensitive, wide bill is its primary navigational tool when feeding underwater. Courtesy of Bernard Fanning.

Figure 3.

The short‐beaked echidna, T. aculeatus. The short‐beaked echidna (T. aculeatus) is characterized by a short, straight beak and by a heavy coat of stout, sharp spines. T. aculeatus uses its beak, massive forearms and spatulate claws to break into ant and termite mounds or rotting logs in search of insect prey. Courtesy of Anne Musser.

Figure 4.

The long‐beaked echidna, Zaglossus bruijnii. The long‐beaked echidna (Z. bruijnii) is the largest living monotreme, up to 17 kg in weight and up to 1 m in length. Its long beak has a marked downward curve, and its spines are smaller and less conspicuous than in T. aculeatus. Courtesy of Timothy Flannery.


Further Reading

Archer M, Flannery TF, Ritchie A and Molnar RE (1985) First Mesozoic mammal from Australia – an early Cretaceous monotreme. Nature 31: 363–366.

Augee ML (ed.) (1992) Platypus and Echidnas. Sydney: The Royal Zoological Society of New South Wales.

Augee M and Gooden B (1993) Echidnas of Australia and New Guinea. Sydney: New South Wales University Press.

Flannery TF (1998) Mammals of New Guinea. Sydney: New Holland Publishers.

Grant TR (1995) The Platypus: A Unique Mammal. Sydney: University of New South Wales Press.

Griffiths M (1968) Echidnas. Oxford: Pergamon Press.

Griffiths M (1978) The Biology of the Monotremes. New York: Academic Press.

Manger PR and Pettigrew JD (eds) (1998) Platypus biology: recent advances and reviews. Philosophical Transactions of the Royal Society of London (B) 353: 1059–1237.

Nicol SC (ed.) (2003) Monotreme Biology, Contributions from a Satellite Symposum of the ICCPB, Tasmania, Australia 2003. Comparative Biochemistry and Physiology Part A 136: 795–963.

Pascual R, Archer M, Ortiz JE et al. (1992) First discovery of monotremes in South America. Nature 356: 704–706.

Rich TH, Hopson JA, Musser AM, Flannery TF and Vickers‐Rich P (2005) Independent origins of middle ear bones in monotremes and therians. Science 307: 910–914.

Rich TH, Vickers‐Rich P, Trusler P et al. (2001b) Monotreme nature of the Australian Early Cretaceous mammal. Teinolophos trusleri. Acta Palaeontologica Polonica 46: 113–118.

Rose RW (ed.) (1998) Special issue: proceedings of a platypus symposium. Australian Mammalogy 20(2): 147–314.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
Musser, Anne M(Sep 2005) Monotremata. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0004128]