 The first is the clade Arctometatarsalia, made up of tyrannosauroids, ornithomimosaurs, and troodontids, because all of these coelurosaurs had pinched middle metatarsal bones in their feet.In this proposed classification system, the tyrannosauroids were supposedly basal to a clade known as Bullatosauria, which was made up of the Troodontidae and the Ornithomimosauria.These two groups were purported to form a clade, because they both shared a common characteristic; which was a skull capsule.