Selene vomer vs horse-head

Selene vomer and horse-head both are nouns.

Word	Noun	Adjective	Verb	Adverb
Selene vomer	Yes	No	No	No
horse-head	Yes	No	No	No

As nouns, horse-head is a hypernym of Selene vomer; that is, horse-head is a word with a broader meaning than Selene vomer:

Selene vomer: similar to moonfish but with eyes high on the truncated forehead
horse-head: any of several silvery marine fishes with very flat bodies

Other hypernyms of Selene vomer include Atlantic moonfish, dollarfish, horsefish, horsehead, moonfish, Selene setapinnis.

Selene vomer (noun)	horse-head (noun)
similar to moonfish but with eyes high on the truncated forehead	any of several silvery marine fishes with very flat bodies