Huh…if marsupials first arose in what is now the Americas, why are modern day American marsupials so…just opossums? I would expect a greater variety where they originated than where they migrated to. Competition from placental mammals not present in Australia?
Yup. As far as I know the placental mammals on Australia arrived there much later so the marsupials had already filled most available niches at that point.
Huh…if marsupials first arose in what is now the Americas, why are modern day American marsupials so…just opossums? I would expect a greater variety where they originated than where they migrated to. Competition from placental mammals not present in Australia?
Yup. As far as I know the placental mammals on Australia arrived there much later so the marsupials had already filled most available niches at that point.