A new Early–Middle Miocene phalangerid (Marsupialia: Phalangeridae) from the Riversleigh World Heritage Area, Boodjamulla (Lawn Hill) National Park, northwestern Queensland

Abstract Archerus johntoniae represents a new genus and species of phalangerid possum from the Early to Middle Miocene of the Riversleigh World Heritage Area, northwestern Queensland. The new taxon is the tenth extinct phalangerid species to be described and is the seventh species recognized from the diverse Riversleigh fossil assemblages. A. johntoniae has its closest morphometric affinities (such as relatively short molars, narrow premolars, an anteriorly narrow upper first molar, and posteriorly narrow fourth molars) with trichosurine and stem phalangerids. Morphologically, A. johntoniae has similarities to phalangerines and trichosurines, but is most dissimilar to other fossil phalangerids. The new species is one of the smallest (ca 1.3 kg) phalangerids known and may have occupied Early and Middle Miocene frugivorous/insectivorous niches demarcated from other phalangerids by body size and diet. A. johntoniae is one of a minority of Riversleigh species to have survived a significant decline in marsupial diversity associated with a rapid spike in global temperature at the Middle Miocene Climatic Optimum. Troy Myers [t.myers@unsw.edu.au], Earth and Sustainability Science Research Centre, School of Biological, Earth & Environmental Sciences, UNSW Sydney, NSW 2052, Australia; Kirsten Crosby [Kirsten.crosby@gmail.com], GHD Group Pty Ltd, Level 15, 133 Castlereagh St, Sydney, NSW, 2000 (currently), School of Biological, Earth & Environmental Sciences, UNSW Sydney, NSW 2052, Australia.