The ichnological record of Australian Cretaceous ornithopodan dinosaurs: diversity, behaviour, and implications for the evolution of pedal posture

Abstract

Australia has a diverse array of ornithopodan dinosaur tracks. As biogenic structures, these tracks have the potential to provide palaeobiological information on the pedal anatomy and posture, locomotor kinematics, behaviour, sociality and environmental preferences of these dinosaurs, in addition to illuminating evolutionary trends within the clade. The aim of this thesis was to critically re-evaluate tridactyl tracks from the Australian Cretaceous that could potentially pertain to ornithopods, to clarify the relationship between the poly-ichnomorphic Wintonopus-Skartopus complex using three-dimensional technology, to describe and interpret new ornithopodan track material from Australia, and to synthesise the implications of these findings for my understanding of ornithopod palaeobiology and evolution. My study focussed on two Australian Cretaceous tracksites, both of which contain an abundance of ornithopodan tracks: Lark Quarry in central-western Queensland (upper Cenomanian-lower Turonian portion of the Winton Formation), and the Dampier Peninsula coastline, north of Broome, Western Australia (Broome Sandstone, Valanginian-Barremian). Although Lark Quarry was extensively researched in the mid 1980's, subsequent studies have only examined the published data rather than the actual track specimens. Earlier research at the Dampier Peninsula coastline hinted at the presence of a highly diverse dinosaurian ichnofauna, including those of ornithopodan origin, yet provided little in the way of detailed ichnotaxomic information. Based on my investigations, I conclude that the largest Lark Quarry tracks are of likely ornithopodan origin based on several lines of evidence: the ichnogenus to which the tracks were originally compared, Tyrannosauropus, is now widely regarded as pertaining to an ornithopodan trackmaker; the original published track outline resemble the ornithopodan ichnospecies Amblydactylus gethingi; multi-bivariate analysis of track length and width ratios derived from the originally published track outlines suggests a trackmaker with ornithopodan affinities; digitally