annelidan vs annelid

annelidan is not a noun while annelid is a noun.

Word	Noun	Adjective	Verb	Adverb
annelidan	No	Yes	No	No
annelid	Yes	Yes	No	No

As adjectives, annelidan and annelid are synonyms defined as:

annelidan and annelid: relating to or belonging to or characteristic of any worms of the phylum Annelida

annelidan (noun)	annelid (noun)
	worms with cylindrical bodies segmented both internally and externally

annelidan (adjective)	annelid (adjective)
relating to or belonging to or characteristic of any worms of the phylum Annelida	relating to or belonging to or characteristic of any worms of the phylum Annelida