My opinion is that dinosaurs were likely present on earth at the same time as the rest of creation, humans included. They were part of God’s creation. Here are a few thoughts to consider. Since dinosaur bones have been discovered in recent times that contain soft tissue it would seem that they may not have died as long ago as was once thought. In the book of Job, God refers to two creatures – Behemoth (ch. 40) and Leviathan (ch. 41) – the description of which sound “dinosaurish.”
Here is another thought – since many of the dinosaurs were reptiles, and since reptiles (unlike mammals) never stop growing and since it appears that life expectancy prior to Noah’s flood in Genesis 6 was far longer than today, just exactly what would a 900 year old lizard look like?
What happened to the dinosaurs? One thought is they perished in the Genesis flood. Since we find many dinosaur bones on higher elevations (not the normal habitat for such creatures) is it possible that with the rising flood waters they were driven higher in an attempt to survive and died in the mountains where their bones continue to be unearthed to this day? Following the flood, life expectancy dropped dramatically. Perhaps the climate also changed dramatically and an environment suitable for these giant beasts no longer existed.
These are just a few of the many thoughts and possible explanations for dinosaurs and the Bible. There is so much more to be said on the subject, but hopefully this brief response will serve as a motivation to explore more about dinosaurs and God’s creation.