decapod crustacean vs decapod

decapod crustacean and decapod both are nouns.

Word	Noun	Adjective	Verb	Adverb
decapod crustacean	Yes	No	No	No
decapod	Yes	No	No	No

As nouns, decapod crustacean and decapod are synonyms defined as:

decapod crustacean and decapod: crustaceans characteristically having five pairs of locomotor appendages each joined to a segment of the thorax

decapod crustacean (noun)	decapod (noun)
crustaceans characteristically having five pairs of locomotor appendages each joined to a segment of the thorax	crustaceans characteristically having five pairs of locomotor appendages each joined to a segment of the thorax
	cephalopods having eight short tentacles plus two long ones