anthozoan vs sea pen

anthozoan and sea pen both are nouns.

Word	Noun	Adjective	Verb	Adverb
anthozoan	Yes	No	No	No
sea pen	Yes	No	No	No

As nouns, sea pen is a hyponym of anthozoan; that is, sea pen is a word with a more specific, narrower meaning than anthozoan:

anthozoan: sessile marine coelenterates including solitary and colonial polyps; the medusoid phase is entirely suppressed
sea pen: fleshy featherlike warm-water colonies

Other hyponyms of anthozoan include anemone, sea anemone, coral.

anthozoan (noun)	sea pen (noun)
sessile marine coelenterates including solitary and colonial polyps; the medusoid phase is entirely suppressed	fleshy featherlike warm-water colonies