 In 1989, scutes which were found in the Kayenta Formation (Glen Canyon Group) of northern Arizona, were by Kevin Padian referred to a Scelidosaurus sp., and used to determine that the age of the strata was around 199.6-196.5 million years ago, at a time when it was still thought that Scelidosaurus harrisonii dated to the early Sinemurian. These scutes established a geographic tie-in between Arizona's Glen Canyon and Europe, where fossils of Scelidosaurus had previously been discovered. Later scientists have rejected the assignment to Scelidosaurus, as the scutes are different in form. In 2014, Roman Ulansky named a new species, S. arizonenesis, based off these specimens. In 2016, Peter Malcolm Galton and Kenneth Carpenter identified it as a nomen dubium, instead once again placing the specimens as Thyreophora indet.
