A new genus and two new species of malleodectid (Marsupialia, Malleodectidae) from the Middle and Late Miocene deposits of the Riversleigh World Heritage Area, northwestern Queensland.

Abstract Isolated upper teeth of a new fourth species of Malleodectes , M. arenai sp. nov. and an isolated lower molar representing a new genus of diminutive malleodectid, Weirdodectes napoleoni sp. nov. are described from Riversleigh’s Middle Miocene deposits. In addition, new malleodectid dental material from Middle and Late Miocene deposits at Riversleigh includes the first lower dentition of Malleodectes mirabilis and the first upper dentition of M. wentworthi . Comparisons of the upper and lower dentitions of M. mirabilis and M. wentworthi with that of the putative dasyurid Barinya wangala suggests that taxon is also a malleodectid. Parsimony and Bayesian phylogenetic analyses support a congeneric relationship between M. mirabilis and M. wentworthi , and support assignment of species of Barinya to Malleodectidae. These analyses support previous studies that found malleodectids were more closely related to dasyurids and myrmecobiids than to thylacinids. The snail-eating hypothesis for malleodectids is restricted to species of Malleodectes , with a more generalised durophagous diet suggested for B. wangala . The diet of Weirdodectes napoleoni sp. nov. is unknown but its dentition suggests it was highly specialised.