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Nature 389, 440-441 (2 October 1997) | doi:10.1038/38891

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Evolutionary biology:  Pelvic problems for mammals

Robert Presley1

Living mammals can be subdivided into the monotremes (which lay eggs), the marsupials (which nurture their young in a pouch) and the placentals (in which the young stay in the uterus until a comparatively late stage of development). Traditionally, the epipubis or so-called 'marsupial bone' has been associated with the suckling of young in a marsupial pouch: its absence from placental mammals supposedly reflected prolonged intrauterine development and birth at a stage when the individual could survive either in a nest or by keeping pace with the mother during lactation.

  1. Robert Presley is in the School of Molecular and Medical Biosciences, Cardiff University of Wales, PO Box 911, Cardiff CF1 3US, UK.