The basic idea of, 'does the Bible mention dinosaurs', is much more complex and far reaching than we may realize. It effects our belief in the actual six day theory of creation, the age of the earth and even evolution as well as other theories. There are those who feel the earth is over 4 billion years old and there are those that use the accounts in Genesis, such as Noah's age, genealogy, the resting of the Ark, etc., to determine the earth being 6,000+ years old. Those who believe in the older age of the earth, tend to hold that the Bible does not mention dinosaurs because dinosaurs were to have died out millions of years before man. Those who believe in the younger age of the earth tend to believe the Bible does mention dinosaurs.
The Bible does not actually use the word "dinosaur". Many Biblical scholars look at the Hebrew word; "tanniyn". It is often translated as "sea monster" or a giant "serpent" but is most commonly thought to mean "dragon". Whatever the translation, it is certainly used to denote a giant reptile. I have read where the KJV of the Old Testament uses tanniyn 28 times: 21 as a dragon, 3 as a serpent, 3 as a whale, and 1 as a sea monster.
Ezekiel 29:3 King James Version (KJV); "Speak, and say, Thus saith the Lord God; 'Behold, I am against thee, Pharaoh king of Egypt, the great dragon that lieth in the midst of his rivers."
Isaiah 27:1 King James Version (KJV); "In that day the Lord with His sore and great and strong sword shall punish leviathan the piercing serpent, even leviathan that crooked serpent; and He shall slay the dragon that is in the sea."
Job 40:15-24 King James Version (KJV) Selected; "Behold now behemoth, which I made with thee; he eateth grass as an ox. Lo now, his strength is in his loins, and his force is in the navel of his belly. He moveth his tail like a cedar: the sinews of his stones are wrapped together. His bones are as strong pieces of brass; his bones are like bars of iron. Surely the mountains bring him forth food, where all the beasts of the field play. Behold, he drinketh up a river, and hasteth not: he trusteth that he can draw up Jordan into his mouth. He taketh it with his eyes: his nose pierceth through snares."
The Hebrew term, tanniyn, applies to some form of a monster, either marine or land. Many scholars believe Scripture writers used tanniyn to describe images of dinosaurs in the Bible.
Even if the Bible does mention dinosaurs; are not dinosaurs supposedly millions of years old and Genesis places the earth at 6,000 ish years old? There have recently been several revelations where dinosaur bones, thought to be millions of years old, have been cut in to, only to reveal tissue that no way could be more than several thousand years old.
This just barely scratches the surface. One thing we must remember:
Genesis 1:1 King James Version (KJV); "In the beginning GOD created the heaven and the earth."