A new diminutive durophagous Miocene dasyuromorphian (Marsupialia, Malleodectidae) from the Riversleigh World Heritage Area, northern Australia

ABSTRACT

Malleodectes? wentworthi, sp. nov. is a highly specialized durophagous marsupial from a Middle Miocene limestone cave deposit in the Riversleigh World Heritage area, northern Australia. It provides the first information regarding the lower dentition of malleodectids, an extinct family of dasyuromorphians. It is also the smallest durophagous member of Metatheria (marsupials and their stem relatives) known to date, with an estimated body mass of ∼70–90 g, an order of magnitude smaller than other known malleodectids (Malleodectes mirabilis and Ma. moenia ∼1 kg). As in other malleodectids, Ma.? wentworthi has a hypertrophied, dome-like premolar specialized for crushing hard foods. Tentative assignment to the genus Malleodectes is based on derived similarities of the premolar and molar dentition to those of larger species of Malleodectes (known only from upper dentitions), and occlusal compatibility. Quantitative morphofunctional analyses of dental indices and mandibular bending strength are congruent with the previously proposed hypothesis that malleodectids may have been uniquely specialized snail-eaters. Maximum parsimony phylogenetic analysis of a 173 morphological character dataset, with a molecular scaffold enforced, placed Ma.? wentworthi within Dasyuromorphia, in a basal polytomy with Dasyuridae and Mutpuracinus archibaldi, to the exclusion of Barinya wangala, Myrmecobiidae and Thylacinidae. Bayesian analysis of a total evidence dataset that combined morphological with nuclear and mitochondrial DNA sequence data places Ma.? wentworthi as a sister taxon to crown-clade Dasyuridae, although support for this relationship is weak.

ACKNOWLEDGMENTS

We thank the Australian Research Council (DP170101420 to MA and SJH), National Geographic Society (Grant to MA and SJH), Riversleigh Society, P. Creaser and the CREATE Fund, K. and M. Pettit, D. and A. Jeanes, the Earth and Sustainability Science Research Centre, UNSW Sydney, Environment Australia, Queensland Parks and Wildlife Service, Queensland Museum, Outback at Isa, the Waanyi Nation of north-western Queensland, and many volunteers and collaborators in and beyond UNSW who have facilitated this project. We thank M. Janiak for assistance with the phylogenetic analyses. Access to the JASMIN supercomputing facility was provided via NERC Standard Grant NE/T000341/1 (to RMDB).

LIST OF SUPPLEMENTARY DATA FILES

S1-Specimens_examined.docx

S2-List_of_Morphological_Characters.docx

S3-Craniodental and Postcranial morphological matrix.nex

S4-Scaffold tree for maximum parsimony.nex

S5-Maximum parsimony tree.nex

S6-Undated total evidence matrix.nex

S7-Undated total evidence tree.con.tre

S8-Dated total evidence matrix.nex

S9-Dated total evidence tree.con.tre

S10-Tip-Node_calibrations_from_Kealy_and_Beck_2017.docx

S11-Age_ranges_for_fossil_taxa_in_TipNode_Calibrations.docx

S12-Log_Transformed_Principal_Component_Analysis.docx

MPT.tre