The imagery on this page is the basis for a paper entitled The Oldest Platypus and its Bearing on Divergence Timing of the Platypus and Echidna Clades, by T. Rowe, T.H. Rich, P. Vickers-Rich, M. Springer and M.O. Woodburne (Proceedings of the National Academy of Sciences 105:1238-1242, 2008). The abstract is as follows:

       Monotremes have left a poor fossil record, and paleontology has been virtually mute during two        decades of discussion about molecular clock estimates of the timing of divergence between the        platypus and echidna clades. We describe new evidence from high-resolution X-ray computed        tomography indicating that Teinolophos, an Early Cretaceous fossil from Australia’s Flat Rocks locality        (121-112.5 Ma), lies within the crown clade Monotremata, as a basal platypus. Strict molecular clock        estimates of the divergence between platypus and echidnas range from 17-80 Ma, but Teinolophos        suggests that the two monotreme clades were already distinct in the Early Cretaceous, and that their        divergence may predate even the oldest strict molecular estimates by at least 50%. We generated        relaxed molecular clock models using three different datasets, but only one yielded a date        overlapping with the age of Teinolophos. Morphology suggests that Teinolophos is a platypus in both        phylogenetic and ecological aspects, and tends to contradict the popular view of rapid Cenozoic        monotreme diversification. Whereas the monotreme fossil record is still sparse and open to        interpretation, the new data are consistent with much slower ecological, morphological, and        taxonomic diversification rates for monotremes than in their sister taxon, the therian mammals. This        alternative view of a deep geological history for monotremes suggests that rate heterogeneities may        have affected mammalian evolution in such a way as to defeat strict molecular clock models and to        challenge even relaxed molecular clock models when applied to mammalian history at a deep temporal        scale.

This specimen, a left dentary, was collected from the Wonthaggi Formation, Bunarong Marine Park, Victoria, Australia. It was made available to The University of Texas High-Resolution X-ray CT Facility for scanning by Dr. Thomas Rich of Museum Victoria. Funding for scanning and image processing was provided by a National Science Foundation Digital Libraries Initiative grant to Dr. Timothy Rowe of The University of Texas at Austin.

This specimen was scanned by Matthew Colbert on 10 October 2005 along the coronal axis for a total of 1293 slices. Each 1024x1024 pixel slice is 0.012 mm thick, with an interslice spacing of 0.012 mm and a field of reconstruction of 11.84 mm.

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None available.