Frontal Bone Anatomy of Teratophoneus Curriei (Theropoda: Tyrannosauridae) From the Upper Cretaceous Kaiparowits Formation of Utah

Abstract

A right frontal bone belonging to the tyrannosaurid theropod Teratophoneus curriei from the Campanian Kaiparowits Formation of Utah provides important anatomical information that is useful in understanding tyrannosaurid taxonomy and relationships. Many aspects of its anatomy indicate a subadult ontogenetic status of this individual, as they compare favorably with subadults of other tyrannosaurids such as Daspletosaurus torosus and Tyrannosaurus rex. This is consistent with the previous interpretation that this individual was subadult, based on different cranial bones such as lacrimal or maxilla. It is likely that a previous assessment of the body mass of this individual was underestimated, and it is presumed here that it was most likely around 1000 kg. This description of the frontal anatomy has several implications for previous works on tyrannosaurid cranial anatomy, and information that corrects aspects of our understanding on tyrannosaurid frontal anatomy is provided. Reanalysis of Nanuqsaurus hoglundi, a tyrannosaurid theropod that has similar frontal morphology with Teratophoneus curriei, implies that parts of its diagnosis are problematic and the proposed evidence for the supposed diminutive body size of this taxon is weak.