walrus vs pinniped mammal

walrus and pinniped mammal both are nouns.

Word	Noun	Adjective	Verb	Adverb
walrus	Yes	No	No	No
pinniped mammal	Yes	No	No	No

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

walrus: either of two large northern marine mammals having ivory tusks and tough hide over thick blubber
pinniped mammal: aquatic carnivorous mammal having a streamlined body specialized for swimming with limbs modified as flippers

Other hypernyms of walrus include pinnatiped, pinniped.

walrus (noun)	pinniped mammal (noun)
either of two large northern marine mammals having ivory tusks and tough hide over thick blubber	aquatic carnivorous mammal having a streamlined body specialized for swimming with limbs modified as flippers