polydactylous vs dactyl

polydactylous is not a noun while dactyl is a noun.

Word	Noun	Adjective	Verb	Adverb
polydactylous	No	Yes	No	No
dactyl	Yes	No	No	No

polydactylous (noun)	dactyl (noun)
	a finger or toe in human beings or corresponding body part in other vertebrates
	a metrical unit with stressed-unstressed-unstressed syllables

polydactylous (adjective)	dactyl (adjective)
of or relating to a person (or other vertebrate) having more than the normal number of digits