mastodont vs proboscidian

mastodont and proboscidian both are nouns.

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

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

mastodont: 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 mastodont include proboscidean.

mastodont (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