brontosaurus vs brontosaur

brontosaurus and brontosaur both are nouns.

Word	Noun	Adjective	Verb	Adverb
brontosaurus	Yes	No	No	No
brontosaur	Yes	No	No	No

As nouns, brontosaurus and brontosaur are synonyms defined as:

brontosaurus and brontosaur: huge quadrupedal herbivorous dinosaur common in North America in the late Jurassic

Other synonyms of brontosaurus include apatosaur, apatosaurus, Apatosaurus excelsus, thunder lizard.

brontosaurus (noun)	brontosaur (noun)
huge quadrupedal herbivorous dinosaur common in North America in the late Jurassic	huge quadrupedal herbivorous dinosaur common in North America in the late Jurassic