No, it is not. A dinosaur is an extinct reptile, a noun, and is a noun adjunct when used with other nouns as in dinosaur bones or dinosaur droppings (coprolites).
colossal fossil
The prepositional phrase is "about dinosaur extinction" and the object is "extinction." The word "dinosaur" is called a "noun adjunct" rather than an adjective.
Dinosaur cat dinosaur dinosaur dinosaur mat.
dinosaur dinosaur dinosaur
Dinosaur fish dinosaur dinosaur.
under the dinosaur
Dinosaur 35 is arrhinosaurus.
The word dinosaur's means "terrible lizard".
as loud as a dinosaur
Barney is a dinosaur from our imagination...
My favourite dinosaur is the triceratops.I had a dinosaur lunch box as a kid.We will take her to the dinosaur museum this weekend.
gertie the dinosaur was famous for being a dinosaur on television