actinozoan vs sea pen

actinozoan and sea pen both are nouns.

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

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

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

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

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