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| Wakaleo schouteni Gillespie, Archer & Hand, 2017 challenging the thylacinid Nimbacinus dicksoni over a kangaroo carcass in the late Oligocene forest at Riversleigh |
Abstract
Wakaleo schouteni sp. nov., a dog-sized marsupial lion (Thylacoleonidae), is described from late Oligocene to early Miocene sediments of the Riversleigh World Heritage Area, Queensland, Australia. Fossils of this new species include a near-complete cranium, dentaries and postcrania. This species is the second thylacoleonid known from late Oligocene sediments. The other, Priscileo pitikantensis Rauscher, 1987, from the Etadunna Formation of South Australia, is known from teeth, part of a palate and postcrania. Wakaleo schouteni exhibits cranial and dental morphology characteristic of species of Wakaleo but possesses a relatively plesiomorphic upper dental formula (i.e. three premolars and four molars) within Thylacoleonidae that was formerly regarded to be diagnostic for species of the genus Priscileo. The holotype and humerus of P. pitikantensis have been compared with the new Wakaleo material described here and found to demonstrate conspicuous similarities in morphology of the M2 and the humerus. In the absence of other generically diagnostic features, Priscileo is here regarded to be a junior synonym of Wakaleo. Smaller size and relatively minor morphological differences in the proximal humerus of W. pitikantensis comb. nov. distinguish it at the specific level from W. schouteni. Phylogenetic analysis of thylacoleonids recovers Wakaleo as a monophyletic clade. Both Wakaleo pitikantensis comb. nov. and W. schouteni are recovered as plesiomorphic sister taxa to other species of the genus. Wakaleo pitikantensis and W. schouteni extend the temporal range for this genus back into the late Oligocene. Body weight for W. schouteni, based on total skull length, is estimated to be ∼23 kg.
Keywords: marsupial lion, Thylacoleonidae, Oligocene–Miocene, taxonomy, Priscileo, Riversleigh
Systematic palaeontology
Class Marsupialia Illiger, 1811
Order Diprotodontia Owen, 1866
Suborder Vombatiformes Woodburne, 1984
Family Thylacoleonidae Gill, 1872
Genus Wakaleo Clemens & Plane, 1974
Type species: Wakaleo oldfieldi Clemens & Plane, 1974
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Included species: Wakaleo vanderleueri Clemens & Plane, 1974; Wakaleo alcootaensis Archer & Rich, 1982; Wakaleo schouteni sp. nov.
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| Reconstruction of Wakaleo schouteni challenging the thylacinid Nimbacinus dicksoni over a kangaroo carcass in the late Oligocene forest at Riversleigh.
(illustration by Peter Schouten).
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Wakaleo schouteni sp. nov.
Derivation of name: Named in honour of Peter Schouten for his exceptional reconstructions of Australia's prehistoric animals, and in particular those from the Riversleigh WHA.
Conclusions
Craniodental and postcranial material of a new marsupial lion, Wakaleo schouteni sp. nov., is described from the Riversleigh WHA. Although this taxon has not reduced/lost the anterior upper premolars, previously regarded to be diagnostic for Wakaleo, it exhibits other Wakaleo apomorphies of the skull and molars. Comparison of the holotype of Priscileo pitikantensis Rauscher, 1987 from the Ngapakaldi LF with Wakaleo schouteni sp. nov. and other Wakaleo species reveals apomorphies of the M2 and similarities in humerus morphology that support its referral to Wakaleo. Priscileo pitikantensis is therefore regarded as a junior synonym of Wakaleo pitikantensis comb. nov. Wakaleo schouteni is distinguished from W. pitikantensis on the basis of its different proximal humerus morphology and larger size, being 10% larger in most dental measures. Markedly different sizes in a sample of humeri of W. schouteni suggest this species was sexually dimorphic. Retention of three upper premolars and four molars are symplesiomorphic features for Wakaleo and Priscileo but distinguish W. pitikantensis and W. schouteni from later species of this genus, all of which exhibit premolar and molar reduction. These two species are the most primitive members of the genus and indicate a pre-late Oligocene origin for the lineage.
Anna K. Gillespie, Michael Archer and Suzanne J. Hand. 2017. A New Oligo–Miocene Marsupial Lion from Australia and Revision of the Family Thylacoleonidae. Journal of Systematic Palaeontology. DOI: 10.1080/14772019.2017.1391885
Fossils of ancient marsupial lion discovered in north-west Queensland
AustralianGeographic.com.au/news/2017/12/fossils-of-ancient-marsupial-lion-discovered-in-north-west-queensland via @AusGeo
AustralianGeographic.com.au/news/2017/12/fossils-of-ancient-marsupial-lion-discovered-in-north-west-queensland via @AusGeo
