I have no clue myself. However, if they were on the Ark it seems to me that it would have been recorded in the Scriptures.They were with everything else in creation, and I believe some were on the ark, but because the entire earth changed post flood, they died off. Since pre flood earth saw no rain, we can suppose that there was a much higher oxygen content on earth, allowing for ability to live longer and to have giant creatures.After the flood, we see the earth as it is today, eliminating some of the larger dinosaurs. For the rest of the kinds of dinosaurs that were smaller in size, they were probably driven to extinction with a growing human population. Every culture, from Asia to South America has stories about giant lizard like critters killing people, I don't think its a coincidence.