sirenian vs aquatic mammal

sirenian and aquatic mammal both are nouns.

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

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

sirenian: any of two families of large herbivorous aquatic mammals with paddle-shaped tails and flipper-like forelimbs and no hind limbs
aquatic mammal: whales and dolphins, manatees and dugongs, walruses, seals

sirenian (noun)	aquatic mammal (noun)
any of two families of large herbivorous aquatic mammals with paddle-shaped tails and flipper-like forelimbs and no hind limbs	whales and dolphins, manatees and dugongs, walruses, seals