mastodon vs proboscidian

mastodon and proboscidian both are nouns.

Word	Noun	Adjective	Verb	Adverb
mastodon	Yes	No	No	No
proboscidian	Yes	No	No	No

As nouns, proboscidian is a hypernym of mastodon; that is, proboscidian is a word with a broader meaning than mastodon:

mastodon: extinct elephant-like mammal that flourished worldwide from Miocene through Pleistocene times; differ from mammoths in the form of the molar teeth
proboscidian: massive herbivorous mammals having tusks and a long trunk

Other hypernyms of mastodon include proboscidean.

mastodon (noun)	proboscidian (noun)
extinct elephant-like mammal that flourished worldwide from Miocene through Pleistocene times; differ from mammoths in the form of the molar teeth	massive herbivorous mammals having tusks and a long trunk