Dinosaur tracks from the Frontier Formation, Montana: preservation, distribution and palaeoecological significance for the middle Cretaceous terrestrial ecosystems of North America

The Coniacian-Santonian stages in western North America are characterized by a sparse fossil record. We present here the first account of dinosaur tracks from nine sites Frontier Formation (Coniacian-Santonian) southwestern Montana. Tracks largely preserved distal alluvial facies as sandstone casts, with single example shallow epirelief impression interpreted undertrack. Sandstone casts show significant relief, kinematic features (i.e., scale marks), and variable morphologies, arguing for strong substrate control on their preservation. Putative producers assigned to ornithopod, ankylosaurian, theropod dinosaurs decreasing order abundance. This record reflects composition similar those other middle Cretaceous formations America. Moreover, ankylosaurian represent known Coniacian strata incorporation body trace fossils yielded indicates presence fauna American endemic elements. establishment dinosaurian palaeocommunities akin observed Campanian Maastrichtian may reflect trend towards provincialism attested end Mesozoic