Atlantic walrus vs walrus

Atlantic walrus and walrus both are nouns.

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

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

Atlantic walrus: a walrus of northern Atlantic and Arctic waters
walrus: either of two large northern marine mammals having ivory tusks and tough hide over thick blubber

Other hypernyms of Atlantic walrus include sea horse, seahorse.

Atlantic walrus (noun)	walrus (noun)
a walrus of northern Atlantic and Arctic waters	either of two large northern marine mammals having ivory tusks and tough hide over thick blubber