A diverse Late Cretaceous vertebrate tracksite from the Winton Formation of Queensland, Australia

Abstract

The Upper Cretaceous ‘upper’ Winton Formation of Queensland, Australia is world famous for hosting Dinosaur Stampede National Monument at Lark Quarry Conservation Park, a somewhat controversial tracksite that preserves thousands of tridactyl dinosaur tracks attributed to ornithopods and theropods. Herein, we describe the Snake Creek Tracksite, a new vertebrate ichnoassemblage from the ‘upper’ Winton Formation, originally situated on Karoola Station but now relocated to the Australian Age of Dinosaurs Museum of Natural History. This site preserves the first sauropod tracks reported from eastern Australia, a small number of theropod and ornithopod tracks, the first fossilised crocodyliform and ?turtle tracks reported from Australia, and possible lungfish and actinopterygian feeding traces. The sauropod trackways are wide-gauge, with manus tracks bearing an ungual impression on digit I, and anteriorly tapered pes tracks with straight or concave forward posterior margins. These tracks support the hypothesis that at least one sauropod taxon from the ‘upper’ Winton Formation retained a pollex claw (previously hypothesised for Diamantinasaurus matildae based on body fossils). Many of the crocodyliform trackways indicate underwater walking. The Snake Creek Tracksite reconciles the sauropod-, crocodyliform-, turtle-, and lungfish-dominated body fossil record of the ‘upper’ Winton Formation with its heretofore ornithopod- and theropod-dominated ichnofossil record.

A nearly complete skull of the sauropod dinosaurDiamantinasaurus matildaefrom the Upper Cretaceous Winton Formation of Australia and implications for the early evolution of titanosaurs

“…Lissamphibians and synapsids are as yet unknown from the Winton Formation, whereas lepidosauromorphs are represented by a single vertebra originally interpreted as a dolichosaurid [ 56 ], but more recently regarded as an indeterminate varanoid [ 57 ]. Although fossil remains of testudinatans (possibly chelids) are seemingly fairly common near both Winton and Eromanga [ 9 , 34 ], the only described evidence for their presence constitutes possible ichnites from near Winton [ 42 ]. Crocodyliforms are well represented near both Isisford and Winton, with the former region producing Isisfordia duncani [ 58 , 59 ], and the latter producing Confractosuchus sauroktonos [ 60 ], as well as several trackways made by swimming or underwater-walking crocodyliforms [ 42 ].…”

“…Although fossil remains of testudinatans (possibly chelids) are seemingly fairly common near both Winton and Eromanga [ 9 , 34 ], the only described evidence for their presence constitutes possible ichnites from near Winton [ 42 ]. Crocodyliforms are well represented near both Isisford and Winton, with the former region producing Isisfordia duncani [ 58 , 59 ], and the latter producing Confractosuchus sauroktonos [ 60 ], as well as several trackways made by swimming or underwater-walking crocodyliforms [ 42 ]. Pterosaurs are rare, with the anhanguerid Ferrodraco lentoni and an isolated anhanguerian femur from near Winton being the only specimens described to date [ 61 – 63 ].…”

“…Vertebrates are represented in the Winton Formation by both body fossils and ichnofossils. Actinopterygians are represented by the ichthyodectiform Cladocyclus geddesi from near Isisford [52], as well as a possible feeding trace from near Winton [42]. Isolated toothplates of two ceratodontoid dipnoan species (Metaceratodus wollastoni and M. ellioti) are known from several widely dispersed localities, [53][54][55], and possible lungfish feeding traces have also been identified near Winton [42].…”

“…Actinopterygians are represented by the ichthyodectiform Cladocyclus geddesi from near Isisford [52], as well as a possible feeding trace from near Winton [42]. Isolated toothplates of two ceratodontoid dipnoan species (Metaceratodus wollastoni and M. ellioti) are known from several widely dispersed localities, [53][54][55], and possible lungfish feeding traces have also been identified near Winton [42]. Lissamphibians and synapsids are as yet unknown from the Winton Formation, whereas lepidosauromorphs are represented by a single vertebra originally interpreted as a dolichosaurid [56], but more recently regarded as an indeterminate varanoid [57].…”

“…Although Cretaceous sedimentary rocks in northeast Australia have produced abundant evidence of sauropod dinosaurs [9,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44], very few cranial elements have been discovered. Indeed, aside from teeth and a dentary fragment [33,35,43], only one partial skull has been described to date: that of a referred specimen of Diamantinasaurus matildae (AODF 0836), which preserves a braincase and several additional cranial remains [38,41].…”