ceratopsian

Of or belonging to the Ceratopsia suborder of dinosaurs.

Triceratops is a ceratopsian dinosaur.

One common ceratopsian feature is a frill extending from the back of the skull.

Any member of this suborder

You know, seeing as you bring up so many groups that people claim "all look alike except for maybe x" but really aren't once you actuall look at them (passerines, hadrosaurs, ceratopsians, etc.), maybe you need to write a book on the subject. It would be a rather interesting read.

Bipedal hadrosaurs, great hulking lambeosaurs, certain rhino-like ceratopsians and relatives of the velociraptors - all large and probably able swimmers - had the greatest success.