 Psittacosaurus and Protoceratops are the most common dinosaurs in the different Mongolian sediments where they are found . Triceratops fossils are far and away the most common dinosaur remains found in the latest Cretaceous rocks in the western United States , making up as much as 5 / 6ths of the large dinosaur fauna in some areas . These facts indicate that some ceratopsians were the dominant herbivores in their environments . 
 Psittacosaurus and Protoceratops <a href='drop_aux' title='1'><mark>are</mark></a>the most common dinosaurs in the different Mongolian sediments where they are found . Triceratops fossils <a href='drop_aux' title='2'><mark>are</mark></a>far and away the most common dinosaur <a href='uninflect' title='3'><mark>remains</mark></a> found in the latest Cretaceous rocks in the western United States , making up as much as 5 / 6ths of the large dinosaur fauna in some areas . These facts indicate that some ceratopsians <a href='uninflect' title='4'><mark>were</mark></a> the dominant herbivores in their environments . 
Psittacosaurus and Protoceratops the most common dinosaurs in the different Mongolian sediments where they are found . Triceratops fossils far and away the most common dinosaur remain found in the latest Cretaceous rocks in the western United States , makin up as much as 5 / 6ths of the large dinosaur fauna in sum areas . dese facts indicate dat some ceratopsians was da dominant herbivores in their environments .