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Nature 387, 549-550 (5 June 1997) | doi:10.1038/42352

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Molecular systematics:  The platypus put in its place

David Penny1 & Masami Hasegawa2

The duck-billed platypus, an egglaying mammal, seems a contradiction in terms — not surprisingly, Richard Owen, a leading nineteenth-century anatomist, refused to believe the first reports from Australia that a platypus in captivity had laid eggs, because the animal is otherwise largely so mammal-like. In a formal sense, the conflicting features were resolved by placing monotremes (platypus and the related spiny anteaters, the echidnas) as the earliest mammalian lineage, pre-dating the later divergence of placental and marsupial (pouched) mammals.

  1. David Penny is in the Departments of Theoretical Biology, and Plant Biology and Biotechnology, Massey University, PO Box 11-222, Palmerston North, New Zealand.
  2. Masami Hasegawa is in the Institute of Statistical Mathematics, 4-6-7 Minami-Azabu, Minato-ku, Tokyo 106, Japan.