Assertion: monotreme | /r/CapableOf | arise in early cretaceous
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text: A platypus tooth has been found in the Palaeocene of Argentina, so one hypothesis is that monotremes arose in Australia in the Late Jurassic or Early Cretaceous, and that some migrated across Antarctica to South America, both of which were still united with Australia at that time; however, several genetic studies suggest an origin in the Triassic.