lancelet vs amphioxus

lancelet and amphioxus both are nouns.

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

As nouns, lancelet and amphioxus are synonyms defined as:

lancelet and amphioxus: small translucent lancet-shaped burrowing marine animal; primitive forerunner of the vertebrates

lancelet (noun)	amphioxus (noun)
small translucent lancet-shaped burrowing marine animal; primitive forerunner of the vertebrates	small translucent lancet-shaped burrowing marine animal; primitive forerunner of the vertebrates