triceratops vs ceratopsian

triceratops and ceratopsian both are nouns.

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

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

triceratops: huge ceratopsian dinosaur having three horns and the neck heavily armored with a very solid frill
ceratopsian: any of several four-footed herbivorous dinosaurs with enormous beaked skulls; of the late Cretaceous in North America and Mongolia

Other hypernyms of triceratops include horned dinosaur.

triceratops (noun)	ceratopsian (noun)
huge ceratopsian dinosaur having three horns and the neck heavily armored with a very solid frill	any of several four-footed herbivorous dinosaurs with enormous beaked skulls; of the late Cretaceous in North America and Mongolia