 Thomas M. Lehman has observed that Corythosaurus hasn 't been discovered outside of southern Alberta even though it is one of the most abundant Judithian dinosaurs in the region . Large herbivores like the hadrosaurs living in North America during the Late Cretaceous had " remarkably small geographic ranges " despite their large body size and high mobility . This restricted distribution strongly contrasts with modern mammalian faunas whose large herbivores ' ranges " typical [ ly ] ... span much of a continent . " 
