(1) The word "Dinosaur" does not exist in the Hebrew language.
(2) Dinosaurs probably died with the flood.
(3) God is more concerned with redeeming man, and that is the purpose of His word.
(4) Many creatures that exist today are not even mentioned in the creation account. Why not argue about why God did not mention them?
(5) John 21:25 says, "And there are also many other things that Jesus did, which if they were written one by one, I suppose that even the world itself could not contain the books that would be written. Amen."
How much more with getting into other things such as dinosaurs?
(6) The Old Testament mentions certain creatures such as "Leviathan" which some people interpret to be dinosaurs.