hadrosaurus vs hadrosaur

hadrosaurus and hadrosaur both are nouns.

Word	Noun	Adjective	Verb	Adverb
hadrosaurus	Yes	No	No	No
hadrosaur	Yes	No	No	No

As nouns, hadrosaurus and hadrosaur are synonyms defined as:

hadrosaurus and hadrosaur: any of numerous large bipedal ornithischian dinosaurs having a horny duck-like bill and webbed feet; may have been partly aquatic

Other synonyms of hadrosaurus include duck-billed dinosaur.

hadrosaurus (noun)	hadrosaur (noun)
any of numerous large bipedal ornithischian dinosaurs having a horny duck-like bill and webbed feet; may have been partly aquatic	any of numerous large bipedal ornithischian dinosaurs having a horny duck-like bill and webbed feet; may have been partly aquatic