A revisiting of an old article, improved a bit.
If you think Maastrichtian dinosaur faunas were isolated from one another, you should see their contemporary mammals, which clearly form faunal units across the continents:
- In Laramidia most mammals were either multituberculates or metatherians, with a few eutherians and relictual symmetrodonts and eutriconodonts thrown in. A similar situation seems to have been going on in Appalachia, considered the craddle of ptilodontoidean diversity, with an alphadontid, herpetotheriid and stagodontid also present as well as a few Protungulatum-like eutherians.
- In Asia, by contrast, djadochtatherioidean multituberculates and eutherians ruled, with only deltatheroideans and a few other carnivorous metatherians present. Hateg Island and other parts of Eastern Europe had a fauna dominated by kogaionid multituberculates with a few eutherians.
- In Indo-Madagascar mammalian faunas were dominated by gondwanatheres and various eutherian lineages, with multituberculates and possible haramiyidans also being present.
- In southern South America dryolestoideans and gondwanatheres are king instead, this dominance perhaps extending into parts of Antarctica.
- We know nothing about Australia’s mammal fauna during the Late Cretaceous, but it was possibly dominated by monotremes and haramiyidans (see Kollikodon reinterpretation), with multituberculates and whatever gave rise to Saint Bathans mammal also being present.
- Mosaic are mostly poorly understood. We know a mixture of eutherian and metatherian faunas in western Europe and northern South America with no multituberculates, a mostly Laramidian assemblage in Mexico with South American taxa like gondwanatheres, an Africa in which the only known land mammal is a gondwanathere but that might also have harboured eutherians, metatherians and dryolestoids.