walrus vs pinniped

walrus and pinniped both are nouns.

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

As nouns, pinniped is a hypernym of walrus; that is, pinniped 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: aquatic carnivorous mammal having a streamlined body specialized for swimming with limbs modified as flippers

Other hypernyms of walrus include pinnatiped, pinniped mammal.

walrus (noun)	pinniped (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