plectognath vs acanthopterygian

plectognath and acanthopterygian both are nouns.

Word	Noun	Adjective	Verb	Adverb
plectognath	Yes	No	No	No
acanthopterygian	Yes	No	No	No

As nouns, acanthopterygian is a hypernym of plectognath; that is, acanthopterygian is a word with a broader meaning than plectognath:

plectognath: tropical marine fishes having the teeth fused into a beak and thick skin covered with bony plates or spines
acanthopterygian: a teleost fish with fins that are supported by sharp inflexible rays

Other hypernyms of plectognath include spiny-finned fish.

plectognath (noun)	acanthopterygian (noun)
tropical marine fishes having the teeth fused into a beak and thick skin covered with bony plates or spines	a teleost fish with fins that are supported by sharp inflexible rays