branchiopod vs branchiopodous

branchiopod is a noun but branchiopodous is not a noun.

Word	Noun	Adjective	Verb	Adverb
branchiopod	Yes	Yes	No	No
branchiopodous	No	Yes	No	No

As adjectives, branchiopod and branchiopodous are synonyms defined as:

branchiopod and branchiopodous: of or relating to or characteristic of the subclass Branchiopoda

Other synonyms of branchiopod include branchiopodan.

branchiopod (noun)	branchiopodous (noun)
aquatic crustaceans typically having a carapace and many pairs of leaflike appendages used for swimming as well as respiration and feeding

branchiopod (adjective)	branchiopodous (adjective)
of or relating to or characteristic of the subclass Branchiopoda	of or relating to or characteristic of the subclass Branchiopoda