Three new thylacinids (Marsupialia, Thylacinidae) from late Oligocene deposits of the Riversleigh World Heritage Area, northwestern Queensland

New thylacinid species of <i>Badjcinus</i>, <i>Nimbacinus</i>, and <i>Ngamalacinus</i> are described from upper Oligocene deposits of the Riversleigh World Heritage Area, northwestern Queensland. <i>Badjcinus timfaulkneri</i>, <i>Nimbacinus peterbridgei</i>, and <i>Ngamalacinus nigelmarveni</i> are among the oldest thylacinids yet known and indicate an earlier diversification of the family than previously understood. Maximum parsimony analysis supports a sister group relationship between <i>Ng. nigelmarveni</i> and <i>Ng. timmulvaneyi</i>, but the relationships of the two other new taxa are unresolved. Bayesian dated total evidence analysis using morphological and molecular data supports the generic assignment of <i>B. timfaulkneri</i> and <i>Ng. nigelmarveni</i> but not that of <i>Ni. peterbridgei</i>. Both phylogenies herein support a taxonomic reassignment of <i>Thylacinus macknessi</i> to the genus <i>Wabulacinus</i>, a conclusion also supported by the results of previous studies. Body mass estimates based on molar size regressions indicate body sizes ranging from 3.7 kg to 11.4 kg for the new thylacinid species. <i>Badjcinus timfaulkneri</i> exhibits an extremely deep jaw compared with other thylacinids, with mandibular bending strength analysis suggesting that it was a highly durophagous carnivore much like the modern dasyurid <i>Sarcophilus harrisii</i>. This analysis also suggests <i>Ni. peterbridgei</i> had a dentary more similar in shape to that of plesiomorphic thylacinid faunivores such as <i>Ni. dicksoni</i> and <i>T. cynocephalus</i> suggesting that it had a relatively more generalist faunivorous diet. The molars of <i>Ng. nigelmarveni</i> suggest they were better suited for longitudinal slicing than the molars of <i>B. timfaulkneri</i> and <i>Ni. peterbridgei</i>, indicating a more hypercarnivorous diet compared with that of those species. http://zoobank.org/urn:lsid:zoobank.org:pub:1BFB344B-8E76-45DC-81ED-18CB4E02D136