Placenta
Volume 29, Issue 11 , Pages 930-931, November 2008

What Fossils Can Tell Us About the Evolution of Viviparity and Placentation

  • A.M. Carter

      Affiliations

    • Corresponding Author InformationTel.: +45 6550 3716; fax: +45 6613 3479.

Department of Physiology and Pharmacology, University of Southern Denmark, J. B. Winsloewvej 21, Third Floor, DK-5000 Odense, Denmark

Accepted 30 July 2008. published online 09 September 2008.

Abstract 

Recently a fossil of one of the earliest jawed fishes was found with a fetal skeleton and the remains of a cord. It was from the Devonian period and takes the history of vertebrate placentation back to 380 million years ago. This and later fossil evidence for viviparity in marine reptiles and early mammals is reviewed. Of particular interest are the fossils of horses as they document that a reproductive strategy with a single precocial newborn was evolved early on. In one instance there is sufficient representation of soft tissue to imply that early horses had a diffuse placenta, much as had been predicted by phylogenetic analyses of placentation.

Keywords: Evolution, Horses, Placentation, Placoderms, Viviparity

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PII: S0143-4004(08)00224-5

doi:10.1016/j.placenta.2008.07.012

Placenta
Volume 29, Issue 11 , Pages 930-931, November 2008

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