Deep time diversity of metatherian mammals: implications for evolutionary history and fossil-record quality

Despite a global fossil record, Metatheria are now largely restricted to Australasia and South America. Most metatherian palaeodiversity studies to date are limited to particular subclades, time intervals and/or regions, and few consider uneven sampling. Here, we present a comprehensive new dataset on metatherian fossil occurrences (Barremian to end-Pliocene). These data are analysed using standard rarefaction and Share-holder Quorum Subsampling (including a new protocol for handling ‘Lagerstätten’-like localities). Global metatherian diversity was lowest during the Cretaceous, and increased sharply in the Paleocene, where the South American record begins. Global and South American diversity rose in the early Eocene then fell in the late Eocene, contrasting the North American pattern. In the Oligocene diversity declined in the Americas but this was more than offset by Oligocene radiations in Australia. Diversity continued to decrease in Laurasia with final representatives in North Ameri...