decapod vs spirula

decapod and spirula both are nouns.

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

As nouns, spirula is a hyponym of decapod; that is, spirula is a word with a more specific, narrower meaning than decapod:

decapod: cephalopods having eight short tentacles plus two long ones
spirula: a small tropical cephalopod of the genus Spirula having prominent eyes and short arms and a many-chambered shell coiled in a flat spiral

Other hyponyms of decapod include squid, cuttle, cuttlefish, Spirula peronii.

decapod (noun)	spirula (noun)
crustaceans characteristically having five pairs of locomotor appendages each joined to a segment of the thorax	a small tropical cephalopod of the genus Spirula having prominent eyes and short arms and a many-chambered shell coiled in a flat spiral
cephalopods having eight short tentacles plus two long ones