We have fossils of other very large creatures from the pre-flood world (dragon flies with a 3 foot wing spread, 6 foot tall rabbits, giant sloth's, etc...). When God told Noah about the coming flood he told Noah to take two of each "kind" of land living, air breathing animal on the ark. This would have included each "kind" of dinosaur. But weren't they too big? Dinosaurs hatch out of eggs and the larger dinosaur eggs are about the size of a football. So even the giant T-Rex was once the size of a small dog soon after he hatched. So space for young ones on the Ark would not be a problem. Each "kind" would represent great variety. For example a pair of dogs would represent the dog kind including wolves, coyotes, dingoes, etc. Not two Great Danes, two Poodles, two Daschund, two Timber Wolves, two Chihuahua, two whatever...
When Noah's flood was over, the earth had changed radically. The lush vegetation was gone. The climate was much more severe. And predatory behavior, animals killing other animals for food, became dominant. So the dinosaurs became extinct because of these new conditions.
In summary, the dinosaurs were created at the same time as Adam, lived in the garden, many were destroyed in Noah's flood, and those that came off the Ark became extinct quickly because of the post flood conditions. Got questions about this?
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Next month we'll answer the question: "Is there any evidence that men encountered dinosaurs?"