Diversity and palaeoecology of Australia's southern-most sauropods, Griman Creek Formation (Cenomanian), New South Wales, Australia

Abstract

Predominately, occurances of Australian sauropods from the Early to mid-Cretaceous of Queensland and Western Australia, lie between ~45° and 55°S palaeolatitude. The Cenomanian Griman Creek Formation, which straddles the New South Wales–Queensland border, preserves arguably one of the richest Cretaceous terrestrial faunas in Australia. Although sauropod postcranial elements are notably absent or as yet unidentified, isolated sauropod teeth are relatively well represented from exposures near Lightning Ridge (New South Wales), offering insights into the diversity and palaeoecology of these animals at ~60°S palaeolatitude. From a sample of 25 teeth, we identify five dental morphotypes from the Griman Creek Formation. Some of this variation is attributed to heterodonty; however, other distinctive morphologies partly agree with previous indications of at least two taxa of non-titanosaur titanosauriforms together with a third, possible titanosaur in the Griman Creek Formation. An investigation of dental microwear found two teeth with identifiable wear features, but differences in these features suggest separate feeding strategies consistent with the hypothesis of ecological tiering between sympatric species. The presence of at least two non-titanosaur titanosauriforms and a third species of titanosaur in the Griman Creek Formation is reminiscent of the roughly coeval Winton Formation in central Queensland, which preserves three titanosauriform species, and implies that diverse sauropod communities persisted during this interval into their most southern recorded range in Australia.