Marsupial responses to global aridification

Perhaps none of Australia's remarkable endemic plants and animals are more iconic than the kangaroos and wallabies that constitute the superfamily Macropodoidea. These pouched animals share a common ancestor with all the world's mammals, but like Australia's other marsupials, they evolved in isolation from small opossum-like founders that inhabited the southern supercontinent of Gondwana in the late Mesozoic [100 to 66 million years (Ma) ago] (1). The evolution of these iconic Australian groups (or clades) offers comparative opportunities for understanding how global-scale processes like climate change interact with the exceedingly contingent processes of evolution, adaptation, and extinction. On page 72 of this issue, Couzens and Prideaux (2) show that dental evolution in kangaroos responded to global aridification much like it did in other mammalian herbivores around the world, but that in Australia, tooth specialization was linked to a late spread of grasslands that postdated the onset of drier habitats.