Classification: Reptiles, lizard-like dinosaurs
Nannotyranus may be an adolescent Tyrannosaurus. Nannotyranus is the smallest known tyrannosaurid and was one of the last tyrannosaurids to live before the Cretaceous Extinction.
Most palaeontologists believe that the skull belongs to an adolescent Tyrannosaurus rex, but there are subtle differences between the two species. Nannotyranus has more teeth and some articulated bones, which Tyrannosaurus does not.
These traits have led palaeontologists to keep the two species separate until more research is done or new specimens are discovered.