Bivalvia vs class Pelecypoda

Bivalvia and class Pelecypoda both are nouns.

Word	Noun	Adjective	Verb	Adverb
Bivalvia	Yes	No	No	No
class Pelecypoda	Yes	No	No	No

As nouns, Bivalvia and class Pelecypoda are synonyms defined as:

Other synonyms of Bivalvia include class Bivalvia, class Lamellibranchia, Lamellibranchia.

Bivalvia (noun)	class Pelecypoda (noun)
oysters, clams, scallops, mussels	oysters, clams, scallops, mussels