Gondwannan Metatherians Redux
So Wilson et al 2016 pretty much vindicated previous finds that the “Gurlin Tsav” skull forms a clade with south american metatherians… and that these are NOT related to marsupials!
Instead, marsupials are part of the extensive north american metatherian radiation that originated in the Campanian and eventually died off in the KT event. This vindicates a north american origin for marsupials, being basically an extension of the Peradectes–Herpetotherium line.
This, however, clearly showed that there was another radiation of southern metatherians, composed of sparassodonts and assorted Paleocene taxa. These instead have as their closest relative the aforementioned asian Gurlin Tsav species, with no currently known close north american relatives.
As previously suggested, an asian origin through India remains untested but likely, somewhere during the Late Cretaceous or early Paleocene. As Australia’s early Cenozoic fossil reccord remains poor, the possibility that these metatherians colonized East Gondwanna first and then became locally extinct is high. Archaeonothos in particular could be a member of this clade, since similarities with sparassodonts are noted.
Wilson, G.P.; Ekdale, E.G.; Hoganson, J.W.; Calede, J.J.; Linden, A.V. (2016). “A large carnivorous mammal from the Late Cretaceous and the North American origin of marsupials”. Nature Communications. 7. doi:10.1038/ncomms13734.
Robin M.D. Beck (2015). “A peculiar faunivorous metatherian from the early Eocene of Australia”. Acta Palaeontologica Polonica 60 (1): 123–129. doi:10.4202/app.2013.0011.