stag's-horn coral vs staghorn coral

stag's-horn coral and staghorn coral both are nouns.

Word	Noun	Adjective	Verb	Adverb
stag's-horn coral	Yes	No	No	No
staghorn coral	Yes	No	No	No

As nouns, stag's-horn coral and staghorn coral are synonyms defined as:

stag's-horn coral and staghorn coral: large branching coral resembling antlers

stag's-horn coral (noun)	staghorn coral (noun)
large branching coral resembling antlers	large branching coral resembling antlers