Abstract

New thylacinid species of Badjcinus, Nimbacinus and Ngamalacinus are described from late Oligocene deposits at the Riversleigh World Heritage Area, northwestern Queensland. Badjcinus faulkneri sp. nov., Nimbacinus bridgei sp. nov., and Ngamalacinus nigelmarvenensis sp. nov., 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 Ng. nigelmarvenensis sp. nov., and Ng. timmulvaneyi, 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 B. faulkneri sp. nov., and Ng. nigelmarvenensis sp. nov., but not that of Ni. bridgei sp. nov. Both phylogenies herein elicit the taxonomic reassignment of Thylacinus macknessi to the genus Wabulacinus, a conclusion 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. Badjcinus faulkneri sp. nov., exhibits an extremely deep jaw compared to other thylacinids, with mandibular bending strength analysis suggesting that it was a highly durophagous carnivore much like the modern Sarcophilus harrisii. This analysis also suggests Ni. bridgei sp. nov., had a dentary more similar in shape to plesiomorphic thylacinid faunivores like Ni. dicksoni and T. cynocephalus suggesting that it had a more generalist faunivorous diet. The molars of Ng. nigelmarvenensis sp. nov., suggests it was more suited to longitudinal slicing than the molars of B. faulkneri sp. nov., and Ni. bridgei sp. nov, indicating a more hypercarnivorous diet compared to these taxa.