Fossil bandicoots (marsupialia, peramelidae) and environmental change during the pleistocene on the darling downs, Southeastern Queensland, Australia

Abstract

Synopsis Systematic collecting from fluviatile Pleistocene fossil deposits of the Darling Downs, southeastern Queensland, Australia, has led to an increase in the region's fossil record of bandicoots. Isoodon obesulus, Perameles bougainville and P. nasuta are reported for the first time in the Darling Downs fossil record. Accelerator mass spectrometry 14C dates based on charcoal from bandicoot fossil‐bearing stratigraphic horizons indicates deposition 45–40 ka. Additional material attributed to the recently described Darling Downs P. sobbei is also described. P. sobbei retains plesiomorphic characters in the upper dentition including reduction of the metaconule on M3 and the lack of posterior cingula on M2 and M3. Phylogenetic interpretation of dental characters suggests that P. sobbei has closer affinities to the Pliocene P. bowensis than to any modern species. The presence of extant species such as P. bougainville and I. obesulus as fossils provides evidence that scrublands and closed woodlands with dense understories existed on the Darling Downs during the Pleistocene. The Darling Downs bandicoot assemblage represents the only known fauna, fossil or modern, where I. obesulus, P. bougainville and P. nasuta occur sympatrically. The Pleistocene Darling Downs may have had a more equable climate than occurs today and a greater range of habitat niches to support such populations. The southern and western contraction of the geographical ranges of I. obesulus and P. bougainville between the Pleistocene and the present was probably the result of significant environmental change that may have involved the contraction of woodlands and expansion of grasslands. The persistence of P. nasuta populations on the Darling Downs from the Pleistocene to the present may reflect that species’ ability to adapt to a wide range of habitats.