Ever been asked that? I have.
Well here's the answer to the existence of Dino's and the explanation for their fossil record. And no it's not Gen. 1:24 though that's a good defense, it's also a rather simple explanation and easy thing to defend. And I don't know about you guys but I like to defend the hard issues. The issues that atheists or evolutionists throw at us. The meaning behind seemingly meaningless sufferings. The purpose of salvation. The explanation that accounts for fossil records. And so on and so forth.
The answer resides in my favorite book of the Bible; Job. Particularly chapters 40 and 41. Chapter 40 speaks of a monster Job calls Behemoth. Many have said the Behemoth is a hippo or elephant However, 40:17, says: "Its tail sways like a cedar; the sinews of its thighs are close-knit." The "cedar" mentioned here refers to the cedars of Lebanon. Which were high priced and luxurious antiquities in Ancient times, measured above timber and often times 130 feet long. What elephant or hippo has a tail that long and tough to penetrate? A Brachiosaurus has a tail 150 feet long. Further, verse 23 speaks to this creatures size and strength, saying "If the river rages, it is not disturbed, it is secure, though the Jordan should surge up to its mouth."
Chapter 41 describes a great and fearsome sea creature which some claim is a whale. However, 41:26, says: "Whoever strikes it with a sword will have no effect, nor with the spear, arrow, or dart." Whales can be pierced, travel in family 'Pods' and when separated fear Great White Sharks. Here in verse 34 Job does not speak of creatures but of a creature who "...beholdeth all high [things]: he [is] a king over all the children of pride." Orcas travel in wolf-pack like Pods and do not as Job says in verse 21 "kindleth coals," with their mouths nor does "a flame goeth out of his mouth." In 2008 Oslo uncovered the fossil record of a Pliosaur Kronosaurus whose teeth were sharp enough to cut through wood and was 50 feet long.
As for the existence of fossils, well fossilization does not take millions of years, under the right conditions a bone could be fossilized. Such as, if it is buried under volcanic ash or is submerged in very deep water.
Gen. Chapter 6 presents the explanation for both the extinction and fossilization of Dino's. The great forty-day-forty-night flood that had Noah building that ark of his, remember that from Sunday school. Now if your thinking, 'The Book of Job comes after the Book of Genesis.' The book of Job is actually one of the oldest books of the Bible and is said to have occurred somewhere in the middle of Genesis.