 By the late 1970s and early 1980s , Hadrosaurus had entered the discussion as a possible synonym of either Kritosaurus , Gryposaurus , or both , particularly in semi @-@ technical " dinosaur dictionaries " . David B. Norman 's The Illustrated Encyclopedia of Dinosaurs , uses Kritosaurus for the Canadian material ( Gryposaurus ) , but identifies the mounted skeleton of K. incurvimanus as Hadrosaurus . One more species was added to Kritosaurus in these years . In 1984 , Argentine paleontologist José Bonaparte and colleagues named Kritosaurus australis for hadrosaur bones from the late Campanian @-@ early Maastrichtian Los Alamitos Formation of Rio Negro , Patagonia , Argentina . This species is now thought to be a synonym of Secernosaurus koerneri . 
