selachian vs elasmobranch

selachian and elasmobranch both are nouns.

Word	Noun	Adjective	Verb	Adverb
selachian	Yes	No	No	No
elasmobranch	Yes	No	No	No

As nouns, selachian and elasmobranch are synonyms defined as:

selachian and elasmobranch: any of numerous fishes of the class Chondrichthyes characterized by a cartilaginous skeleton and placoid scales: sharks, rays, skates

selachian (noun)	elasmobranch (noun)
any of numerous fishes of the class Chondrichthyes characterized by a cartilaginous skeleton and placoid scales: sharks, rays, skates	any of numerous fishes of the class Chondrichthyes characterized by a cartilaginous skeleton and placoid scales: sharks, rays, skates