Specimens identified as Nanotyrannus have been reported to show, relative to Tyrannosaurus rex, proportionally longer forearms, fewer tail vertebrae, and a greater number of teeth.
high
morphological
Reported anatomical differences cited in comparative studies of small-bodied tyrannosaur specimens versus T. rex.
Skull characters such as bone structure, cranial nerve pathways, and sinus morphology can provide diagnostic evidence for distinguishing dinosaur species and are not necessarily explained by ontogenetic (age-related) change alone.
high
morphological
Comparative cranial anatomy is used to differentiate species-level versus growth-related variation in fossil theropods.