Elasmobranchii vs subclass Selachii

Elasmobranchii and subclass Selachii both are nouns.

Word	Noun	Adjective	Verb	Adverb
Elasmobranchii	Yes	No	No	No
subclass Selachii	Yes	No	No	No

As nouns, Elasmobranchii and subclass Selachii are synonyms defined as:

Other synonyms of Elasmobranchii include Selachii, subclass Elasmobranchii.

Elasmobranchii (noun)	subclass Selachii (noun)
sharks, rays, dogfishes, skates	sharks, rays, dogfishes, skates