ceratopsian vs ornithischian

ceratopsian and ornithischian both are nouns.

Word	Noun	Adjective	Verb	Adverb
ceratopsian	Yes	No	No	No
ornithischian	Yes	No	No	No

As nouns, ornithischian is a hypernym of ceratopsian; that is, ornithischian is a word with a broader meaning than ceratopsian:

ceratopsian: any of several four-footed herbivorous dinosaurs with enormous beaked skulls; of the late Cretaceous in North America and Mongolia
ornithischian: herbivorous dinosaur with a pelvis like that of a bird

Other hypernyms of ceratopsian include ornithischian dinosaur.

ceratopsian (noun)	ornithischian (noun)
any of several four-footed herbivorous dinosaurs with enormous beaked skulls; of the late Cretaceous in North America and Mongolia	herbivorous dinosaur with a pelvis like that of a bird