|Source: InfoMofo, CC BY-SA 2.0, via flickr|
How do you know dinosaurs survived the flood, and what made them go extinct?
The Bible tells us that at least two of every animal "in whose nostrils was the breath of life" (Genesis 7:22), was saved in the Ark. Therefore, we can be certain that there were dinosaurs on the Ark, and that they survived the flood.
What happened to them afterwards? Well, the same thing that happened to the saber-toothed tiger, the Dodo and the passenger pigeon. Climate, natural disasters or predators (perhaps all three), conspired to wipe them off the face of the earth. The Ice Age, following immediately after the flood, must have been hard on them, as well as all the volcanic activity happening at that time.
Why doesn't the Bible mention dinosaurs?
It would be something of a wonder if the Bible did, since the word “dinosaur” wasn't invented until 1841, over a thousand years after the last books of the Bible were written. What the Bible does mention is something called a “dragon.” And the further back you go in history, the more accounts of “dragons” you find, and often in quite prosaic situations. Old accounts of dragons mention them eating cattle and stealing sheep, not eating dwarves and stealing gold.
Not only does the Bible mention dragons, but God's description of the large "behemoth" in Job 40:15-24 sounds a lot like a large sauropod.
There are reports from all around the world of dinosaurs existing side by side with humans after the flood. Interested? You can find a few of them here.
How did the dinosaurs fit on the Ark?
A very good question, with a very simple answer. Noah would have taken young dinosaurs on the ark, not huge full-grown ones. A newly hatched Sauropod weighted only 11lbs., and was not much bigger than a large goose—the ones Noah brought were certainly bigger than that, but still very small compared with an adult.