Ankylosaur Footprints

Paleontologists have discovered 100-million-year-old fossilized footprints in the Canadian Rockies that reveal the first known tracks of three-toed, clubbed-tail armored dinosaurs, filling a gap in the fossil record. 

The footprints belong to an ankylosaurid, part of a larger group of ankylosaur dinosaurs (see overview) that were heavily armored herbivores from the Late Jurassic to Cretaceous periods, known for their bony plates (even on their eyelids) and spikes. The ankylosaurs have two main subgroups: the nodosaurids, which have a flexible tail and four toes and whose footprints are well known, and the ankylosaurids, which have sledgehammer-like tails and three toes. Ankylosaurs are estimated to have been up to 30 feet long and weighed over 10,000 pounds. 

The footprints (see photos) from the middle of the Cretaceous period, roughly 100 to 94 million years ago, indicate ankylosaurids were present in North America despite the absence of skeletal remains. The discovery suggests both nodosaurids and ankylosaurids coexisted in the same region during the same period.