Abstract
THE Order Symmetrodonta consists of small Mesozoic therian mammals with tricuspid molars of pretribosphenic type. The order includes species probably ancestral to Jurassic eupantotheres1 and hence to marsupials (Metatheria) and placentals (Eutheria), and it includes less central lineages that have left no known descendants. Symmetrodont fossils are uncommon, and those that are found are mostly fragmentary jaws with teeth. The geologically oldest symmetrodonts are from the Rhaetic of Wales (Kuehneotherium2); Upper Jurassic (Spalacotherium, Tinodon, Eurylambda, Amphidon) and Lower Cretaceous (Spalacotherium, Spalacotheraides, Manchurodon) symmetrodonts are known from Eurasia and North America3–7. Here I report the discovery of the first Upper Cretaceous symmetrodont, from the early Campanian8 Upper Milk River Formation9, Alberta, Canada.
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FOX, R. An Upper Cretaceous Symmetrodont from Alberta, Canada. Nature 239, 170–171 (1972). https://doi.org/10.1038/239170b0
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DOI: https://doi.org/10.1038/239170b0
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