Nouns ending in -ure are usually feminine, but le dinosaure is masculine.
Dinosaure is one of the rare exceptions: learn it as it is.
Is dinosaure masculine or feminine?
ledinosaureexception
The rule behind it
94.3% of -ure nouns are feminine
In context
Les oiseaux ont évolué à partir des dinosaures.
Birds evolved from dinosaurs.
Les élèves ont visité le parc des dinosaures.
The students visited the dinosaur park.
Les dinosaures étaient des animaux à sang chaud.
Dinosaurs were warm-blooded.