Revised age and palaeoecology of the dinosaur-bearing Griman Creek Formation at Lightining Ridge, NSW, Australia

Terrestrial vertebrates are poorly known from the Australian Cretaceous, limited to only a handful of formations continent wide. The Griman Creek Formation (GCF.), which crops out in north-central New South Wales near the town of Lightning Ridge, is noteworthy for the unusual opalized preservation of its fauna as well as being the only dinosaur-bearing terrestrial unit in the state. New U-Pb age dating of detrital zircons extracted from a layer of distal volcanic ashfall, immediately overlying the main fossil-bearing layer revise the maximum depositional age to early- to mid-Cenomanian, rather than late Albian as was previously thought. The new date provides a reliable context for the GCF. fauna for the first time, placing it temporally within the fossiliferous portion of the Winton Formation in central Queensland. More specifically, the Lightning Ridge exposures of the GCF. sit between (with some very minor overlap) the older Albian (Isisford and Longreach sites) and younger Cenomanian to Turonian (Lark Quarry, Bladensburg, and Eromanga) sites within the Winton Formation. These new constraints also permit more meaningful comparisons between the GCF. and Winton faunas. A review of the GCF. vertebrate fauna exposes a diversity of dipnoans, chelid and possible meiolaniform turtles, leptocleidid-like and possible elasmosaurid plesiosaurians, anhanguerian pterosaurs, titanosauriform sauropods, megaraptoran theropods, ankylosaurians, iguanodontians, crocodylomorphs, and rare elements of aspidorhynchid teleosts, lamniform chondrychthians, enantiornithine birds, stem and true monotremes, and a possible indeterminate synapsid, making it one of the most diverse mid-Cretaceous terrestrial vertebrate faunas in Australia. Grant Information