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Aspects of the results of studies of the fossil-rich Cainozoic deposits of Riversleigh, northwestern Queensland, are reviewed. A summary of five selected Riversleigh faunas representing the prirnaryperiods of the region's Cainozoic histoy is provided. Faunal and environmental changes over the last 25 000 000 years in the Riversleigh region are identified and changes in Australia 's rainforest mammal communities over the same period are discussed. Evidence for the origin of Australia's modem mammal groups from ancestors now known to have lived in the Tertiary rainforests of northern Australia is reviewed. The geological record for Riversleigh's more than 100 local faunas is considered. At least three primary intervals of Oligo-Miocene deposition, one of Pliocene and many of Pleistocene and Holocene deposition are identified. An appendix is provided in which the principal faunal assemblages from Riversleigh are allocated to these depositional intervals. The evidence for correlating Riversleigh local faunas with faunal assemblages in the rest of Australia and the world is reviewed. Oligo-Miocene, Pliocene and Pleistocene marsupial and monotreme fossds correlate Riversleigh's local faunas with others kom central and eastern Australia; bats correlate them with faunal assemblages in Europe; rodents correlate them with Pliocene assemblages in eastern Australia.

BackgroundWe describe new cranial and post-cranial marsupial fossils from the early Eocene Tingamarra Local Fauna in Australia and refer them to Djarthia murgonensis, which was previously known only from fragmentary dental remains.Methodology/Principal FindingsThe new material indicates that Djarthia is a member of Australidelphia, a pan-Gondwanan clade comprising all extant Australian marsupials together with the South American microbiotheres. Djarthia is therefore the oldest known crown-group marsupial anywhere in the world that is represented by dental, cranial and post-cranial remains, and the oldest known Australian marsupial by 30 million years. It is also the most plesiomorphic known australidelphian, and phylogenetic analyses place it outside all other Australian marsupials.Conclusions/SignificanceAs the most plesiomorphic and oldest unequivocal australidelphian, Djarthia may approximate the ancestral morphotype of the Australian marsupial radiation and suggests that the South American microbiotheres may be the result of back-dispersal from eastern Gondwana, which is the reverse of prevailing hypotheses.