An upper Coniacian (Upper Cretaceous) dinosaur track record from a high-latitude delta plain setting, north-east British Columbia, Canada

At a palaeolatitude of 58–59°N, sandstones of the upper Coniacian Marshybank Formation represent a delta that prograded into the Western Interior Seaway. Overlying delta plain deposits represent lakes, mires, floodplains, crevasse splays and anastomosed rivers. Ubiquitous root traces in delta plain sediments indicate dense vegetation. Dinosaur tracks, all isolated specimens, and preserved primarily as natural casts and transmitted undertracks, are most commonly found on the base of, and within, crevasse splay sandstones throughout the ~12 m thick delta plain succession, with additional examples in channel bar sandstones. Of a total of 19 tracks, of no more than ‘moderate’ fidelity, 11 are blunt-toed and tridactyl, up to about 45 cm wide and 35 cm long, and are tentatively assigned to the pes tracks of ornithopods. Only one track is of sufficient fidelity to justify attribution to Hadrosauropodus, whereas two subtly arcuate, ovoid structures might represent ornithopod manus tracks. Of four tridactyl tracks with narrow digits, two are assigned with confidence to a theropod, whereas two, of lower fidelity, are of possible theropod origin. Only two, low fidelity tracks with four or five blunt digits might be attributed to the pes and manus of an ankylosaurine dinosaur. Marshybank Formation sediments preserve the stumps and fronds of conifers as well as cycads, ferns and a variety of angiosperms. Dinosaur tracks (and skeletal material) are particularly rare in terrestrial rocks of Coniacian age throughout the Western Interior Seaway. The ornithopod-dominated ichnofauna of the Marshybank Formation preserves the only evidence of Coniacian dinosaurs north of south-western Montana, and contrasts markedly with the ankylosaur-dominated fauna of the underlying Cenomanian rocks of the Dunvegan Formation.