Fossil Record Life History Systematics Morphology

Monotremata: Systematics

Monotremes are mammals. Unlike other mammals monotremes lay eggs, as did the ancestors of the mammals. For this reason, the Monotremata are considered the sister group to all other mammals.

Living monotremes are classified in two families, the Ornithorhynchidae (platypus family) and the Tachyglossidae (echidnas). A summary of living and fossil species currently recognized follows (an asterisk indicates a species which has gone extinct).

Kollikodon ritchiei *

Steropodon galmani *

Monotrematum sudamericanum *
Obdurodon dicksoni *
Obdurodon insignis *
Ornithorynchus anatinus (modern platypus)

Megalibgwilia ramsayi *
Megalibgwilia robusta *
Tachyglossus aculeata (short-nosed echidna)
Zaglossus bruijnii (Western long-beaked echidna)
Zaglossus bartoni (Eastern long-beaked echidna)
Zaglossus attenboroughi (Sir David's long-beaked echidna)
Zaglossus hacketti *


  • Flannery, T.F. and Groves, C.P. 1998. A revision of the genus Zaglossus (Monotremata, Tachyglossidae), with description of new species and subspecies. Mammalia, 62(3): 367-396.
  • Flannery, T.F., M. Archer, T.H. Rich, and R. Jones. 1995. A new family of monotremes from the Cretaceous of Australia. Nature 377:418–420.

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