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. http://zoobank.org/urn:lsid:zoobank.org:pub:9302B839-4F3B-46E9-9F37-A992BC93FC1D SUPPLEMENTAL DATA-Supplemental materials are available for this article for free at www.tandfonline.com/UJVP.

Comparative three‐dimensional jaw muscle anatomy of marsupial carnivores (Dasyurus spp.) and the termite‐eating numbat (Myrmecobius fasciatus)

“…Phylogenetic tree of the Dasyuromorphia (modified from Churchill et al 2022) with illustrations of species investigated in this study, the numbat Myrmecobius fasciatus (above; modified from an original photograph by M. Pot, Martybugs at en.wikipedia under a Creative Commons licence) and the spotted‐tail quoll Dasyurus maculatus (below; modified from original photographs by C. Dingle and R. Craig).…”

“…All other extant Dasyuromorphians belong within the Dasyuridae, ranging from diminutive forms such as Planigale and Ningaui species that weigh less than 10 g in body mass, and slightly larger Sminthopsis , Parantechinus, Dasycercus and Phascogale species, through to cat‐sized Dasyurus species and the Tasmanian devil ( Sarcophilus harrisii ). Two other families, Thylacinidae and the obscure Malleodectidae that were adapted for snail‐eating, are wholly extinct (Churchill et al, 2022; Rovinsky et al, 2019). Dental and basicranial differences of the numbat indicate an early divergence of Myrmecobiidae from the dasyurid lineage.…”