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A Middle Jurassic mammal from Madagascar


The lower molars of tribosphenic mammals (marsupials, placentals and their extinct allies) are marked, primitively, by a basined heel (talonid) acting as the mortar to the pestle of a large inner cusp (protocone) on the opposing upper teeth. Here we report the earliest tribosphenic mammal found so far, three lower teeth in a jaw fragment from Middle Jurassic (Bathonian, 167 ± 2 Myr)1 sediments of northwest Madagascar. This specimen extends the stratigraphic range of the Tribosphenida by some 25 million years, more than doubling the age of the oldest mammal known from Madagascar2, and representing only the second pre-Plio/Pleistocene terrestrial mammal known from the island. Although it indicates a more ancient diversification of the Triposphenida than previously thought, this find fails to confirm molecular-clock-based models proposing a Middle Jurassic divergence of marsupials and placentals3. In addition, it offers a glimpse of mammal evolution on the southern continents during the Middle through Late Jurassic, countering the prevailing view4 of a northern origin for tribosphenic mammals.

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Figure 1: Chronology and phylogenetic relationships of selected tribosphenidans and near-holothere allies.
Figure 2: Posterior tooth (m2) of the holotype of A. mahabo.
Figure 3: The holotype of A. mahabo in occlusal views.


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This work was supported by the National Geographic Society, Field Museum of Natural History and the Unviersity of California. We thank the Ministre de L'Energie et des Mines of Madagascar for authorizing this work, S. Goodman and M. Ravokatra for help with our field efforts and G. Ravololonarivo Randria and A. Rasoamiaramanana. Field Museum volunteers D. Kinzig and R. Chisholm found this specimen during washing and microscope sorting of the matrix; K. Mazanek and M. Donnelly produced the illustrations; R. Andriantompohavana, L. Razafimanantso, A. Toto Volahy and A. Gandie aided us in the field; and W. Clemens and A. Smith provided advice.

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Correspondence to André R. Wyss.

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Flynn, J., Parrish, J., Rakotosamimanana, B. et al. A Middle Jurassic mammal from Madagascar. Nature 401, 57–60 (1999).

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