Early Eocene pelodryadid from the Tingamarra Local Fauna, Murgon, southeastern Queensland, Australia, and a new fossil calibration for molecular phylogenies of frogs

The origins and evolution of Australian frogs are poorly understood. The modern Australian frog fauna is diverse and thought to be derived from South America and later from Asia, but its fossil record is relatively sparse. Molecular phylogenies have identified the early Eocene as a potentially important time for the dispersal of hylids into Australia from South America via Antarctica, as well as the diversification of Australia’s earliest frogs. Herein, we describe a new fossil frog from the lower Eocene fossil site of Tingamarra, at Murgon in southeastern Queensland, Australia. We use micro-computed tomography scans and three-dimensional geometric morphometrics to compare the shape of the diagnostic ilium of the new Tingamarra fossil frog with those from four Gondwanan families. Concordance of morphometric and morphological comparisons reveals that this Tingamarra fossil frog ilium likely represents a new species of pelodryadid frogs referable to the genus Litoria, making it Australia’s earliest known pelodryadid. All known Australian fossil frogs identifiable to genus or species have proven to be most closely related to extant congeners. The Tingamarra Litoria tylerantiqua sp. nov. suggests that pelodryadids were present in Australia by the early Eocene, when the continent was still connected to Antarctica and South America as the last remnants of Gondwana, and also provides a potential new fossil calibration for molecular phylogenies of pelodryadids and frog phylogenies more broadly.