urochord vs larvacean

urochord and larvacean both are nouns.

Word	Noun	Adjective	Verb	Adverb
urochord	Yes	No	No	No
larvacean	Yes	No	No	No

As nouns, larvacean is a hyponym of urochord; that is, larvacean is a word with a more specific, narrower meaning than urochord:

urochord: primitive marine animal having a saclike unsegmented body and a urochord that is conspicuous in the larva
larvacean: any member of the class Larvacea

Other hyponyms of urochord include ascidian, salp, salpa, doliolum, appendicularia.

urochord (noun)	larvacean (noun)
a notochord of a larval tunicate typically confined to the caudal region	any member of the class Larvacea
primitive marine animal having a saclike unsegmented body and a urochord that is conspicuous in the larva