Three new malleodectids (Marsupialia, Malleodectidae) from the late Oligocene and early Miocene deposits of the Riversleigh World Heritage area, northwestern Queensland

Three new malleodectids (Malleodectidae, Marsupialia) are described from late Oligocene and early Miocene deposits of the Riversleigh World Heritage Area, northwestern Queensland. <i>Exosmachus robinbecki</i> gen. et sp. nov. and <i>Chitinodectes wessechresti</i> gen. et sp. nov. share dental synapomorphies with <i>Malleodectes</i> species to the exclusion of other malleodectids. <i>Protamalleus stevewroei</i> gen. et sp. nov. is the most plesiomorphic malleodectid known, retaining several symplesiomorphies shared with plesiomorphic dasyuromorphians and australidelphians. Estimated body masses are 110–155 g (<i>Exosmachus robinbecki</i>), 151 g (<i>Chitinodectes wessechresti</i>), and 226 g (<i>Protamalleus stevewroei</i>). Parsimony phylogenetic analysis supports all new taxa as malleodectids, placing <i>Exosmachus robinbecki</i> as sister to <i>Malleodectes</i> species, <i>Chitinodectes wessechresti</i> as sister to this clade, and <i>Protamalleus stevewroei</i> as sister to all other malleodectids. <i>Barinya wangala</i> is sister to the clade containing <i>Chitinodectes wessechresti</i>, <i>Exosmachus robinbecki</i> and <i>Malleodectes</i>. A Bayesian total evidence analysis places <i>B. wangala</i>, <i>Chitinodectes wessechresti</i>, <i>Exosmachus robinbecki</i>, and <i>Malleodectes</i> within Malleodectidae, but recovers <i>Protamalleus stevewroei</i> as an incertae sedis dasyuromorphian. Morphofunctional analyses suggest <i>Chitinodectes wessechresti</i> and <i>Exosmachus robinbecki</i> were durophagous hypocarnivores like species of <i>Malleodectes</i> species, whereas <i>Protamalleus stevewroei</i> and <i>B. wangala</i> were more generalist carnivores, comparable to <i>Dasyurus viverrinus</i> but with enhanced durophagous capabilities.