Nanotyrannus lancensis
Late Cretaceous (Maastrichtian)
Hell Creek Formation
Billings
Montana USA.

A tooth from Nanotyrannus lancensis is one of the more debated dinosaur fossils in paleontology. Nanotyrannus was described from Late Cretaceous Period rocks — especially the Lance Formation of Wyoming and equivalent Hell Creek deposits in the western United States — dating to roughly 67–66 million years ago.
29mm tooth