heterostracan vs agnathan

heterostracan and agnathan both are nouns.

Word	Noun	Adjective	Verb	Adverb
heterostracan	Yes	No	No	No
agnathan	Yes	No	No	No

As nouns, agnathan is a hypernym of heterostracan; that is, agnathan is a word with a broader meaning than heterostracan:

heterostracan: extinct jawless fish with the anterior part of the body covered with bony plates; of the Silurian and Devonian
agnathan: eel-shaped vertebrate without jaws or paired appendages including the cyclostomes and some extinct forms

Other hypernyms of heterostracan include jawless fish, jawless vertebrate.

heterostracan (noun)	agnathan (noun)
extinct jawless fish with the anterior part of the body covered with bony plates; of the Silurian and Devonian	eel-shaped vertebrate without jaws or paired appendages including the cyclostomes and some extinct forms