Nearly all dinosaurs discovered share certain modifications to the ancestral archosaurian skeleton, or are clearly descendants of older dinosaurs showing these modifications. Although some later groups of dinosaurs featured further modified versions of these traits, they are considered typical for Dinosauria. The earliest dinosaurs had them and passed them on to their descendants.

One such notable trait shared by almost all dinosaurs is that the radius, a lower arm bone, is shorter than 80% of humerus length.