amphioxus vs cephalochordate

amphioxus and cephalochordate both are nouns.

Word	Noun	Adjective	Verb	Adverb
amphioxus	Yes	No	No	No
cephalochordate	Yes	No	No	No

As nouns, cephalochordate is a hypernym of amphioxus; that is, cephalochordate is a word with a broader meaning than amphioxus:

amphioxus: small translucent lancet-shaped burrowing marine animal; primitive forerunner of the vertebrates
cephalochordate: fish-like animals having a notochord rather than a true spinal column

amphioxus (noun)	cephalochordate (noun)
small translucent lancet-shaped burrowing marine animal; primitive forerunner of the vertebrates	fish-like animals having a notochord rather than a true spinal column