dugong vs sirenian mammal

dugong and sirenian mammal both are nouns.

Word	Noun	Adjective	Verb	Adverb
dugong	Yes	No	No	No
sirenian mammal	Yes	No	No	No

As nouns, sirenian mammal is a hypernym of dugong; that is, sirenian mammal is a word with a broader meaning than dugong:

dugong: sirenian tusked mammal found from eastern Africa to Australia; the flat tail is bilobate
sirenian mammal: any of two families of large herbivorous aquatic mammals with paddle-shaped tails and flipper-like forelimbs and no hind limbs

Other hypernyms of dugong include sea cow, sirenian.

dugong (noun)	sirenian mammal (noun)
sirenian tusked mammal found from eastern Africa to Australia; the flat tail is bilobate	any of two families of large herbivorous aquatic mammals with paddle-shaped tails and flipper-like forelimbs and no hind limbs