urochord vs salpa

urochord and salpa both are nouns.

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

As nouns, salpa is a hyponym of urochord; that is, salpa 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
salpa: minute floating marine tunicate having a transparent body with an opening at each end

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

urochord (noun)	salpa (noun)
a notochord of a larval tunicate typically confined to the caudal region	minute floating marine tunicate having a transparent body with an opening at each end
primitive marine animal having a saclike unsegmented body and a urochord that is conspicuous in the larva