A new thyreophoran ichnotaxon from British Columbia, Canada confirms the presence of ankylosaurid dinosaurs in the mid Cretaceous of North America

Abstract

A new thyreophoran trackway morphotype with tridactyl pes tracks is assigned to the new ichnospecies Ruopodosaurus clava ichnogen. et ichnosp. nov. This morphotype differs from the well-known ankylosaurian ichnospecies Tetrapodosaurus borealis, which is characterized by tetradactyl pes tracks and has been widely reported from the Cretaceous of North America. Among ankylosaurs, only ankylosaurids have three pedal digits rather than four, making this the first known track morphotype for ankylosaurid ankylosaurs. This new taxon is currently known exclusively from the Cenomanian of northeastern British Columbia and northwestern Alberta, and provides confirmation that ankylosaurid ankylosaurs were present in North America prior to the Campanian–Maastrichtian. Ruopodosaurus clava is found in the same localities and deposits as Tetrapodosaurus borealis, indicating that both ankylosaurid and non-ankylosaurid ankylosaurs co-existed in the mid Cretaceous of the Peace Region.