Selachii vs Elasmobranchii

Selachii and Elasmobranchii both are nouns.

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

As nouns, Selachii and Elasmobranchii are synonyms defined as:

Other synonyms of Selachii include subclass Elasmobranchii, subclass Selachii.

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