This question presupposes a young earth on which dinosaurs and humanity coexisted and a global flood in the time of Noah. Not all Christians hold to both, or either, of those viewpoints. So, this is not a question that is relevant for all Christians. However, we believe that, if the Bible is interpreted literally, it leads to young earth creationism and a belief that the flood in the time of Noah was indeed global. So, with that in mind, yes, we believe that there were dinosaurs on the ark. They would not have been called “dinosaurs” because that term didn’t exist until about 1841. Here are some reasons why we think that dinosaurs were on Noah’s ark:
We know that “in six days the LORD made the heavens and the earth, the sea, and all that is in them” (Exodus 20:11). Taking these days to be literal, twenty-four-hour periods, the dinosaurs would have been created on day six with the rest of the land animals (Genesis 1:24–25). Man was created on the same day (verses 26–27). There is nothing in the Bible that suggests a separation of millions of years between the time of the dinosaurs and the existence of mankind. The descriptions of the behemoth and leviathan in Job 40 — 41 lend credence to the idea that men and dinosaurs walked the earth together.
Also arguing for the possibility that dinosaurs and man lived side by side—and thus were on Noah’s ark—are ancient depictions of dinosaur-like animals in cave drawings. Various ancient civilizations in Europe, South America, and North America left behind petroglyphs of what look like dinosaurs. We also see dinosaur-like creatures depicted in architecture on castles in Europe and pyramids in South America. We read accounts of human interaction with “dragons,” with the stories coming from Europe, China, and the Middle East. It would be strange for all of these different civilizations to depict things that no one had ever seen, especially since the depictions closely resemble the fossil remains that we now find.
The account of Noah and the ark is found in Genesis 6 — 7. God tells Noah that he is to take representatives of every living creature on board: “You are to bring into the ark two of all living creatures, male and female, to keep them alive with you. Two of every kind of bird, of every kind of animal and of every kind of creature that moves along the ground will come to you to be kept alive” (Genesis 6:19–20). If dinosaurs were on the earth at that time, then Noah took them on the ark.
A common objection to the idea that there were dinosaurs on the ark—besides the view that humans and dinosaurs never existed at the same time—is that dinosaurs were too big for the ark. The notion that all dinosaurs were three stories tall, of fierce disposition, and bent on eating everything in sight persists in the minds of many. That fact is that the average size of adult dinosaurs was comparable to that of a horse.
But most of the dinosaurs on Noah’s ark would have been even smaller than a horse. To start a new population of animals, Noah would not have begun with old animals past their prime. He would have started with the younger (and therefore smaller) animals of each kind. That huge Apatosaurus skeleton that we see in the museum could have been from an animal several hundred years old. A dinosaur of such size and age would not have been a good candidate for breeding stock for Noah. Noah would naturally have taken juvenile Apatosauruses aboard the ark. Reptiles can mature in less than six months, so, even if the dinosaurs Noah took on board were one year old, most would have been smaller than a full-grown pig. That would mean that there was plenty of room for them (and for their food) on the ark.
Since the Bible does not clearly state that what we call dinosaurs were on the ark, we leave open the possibility that they were not. But, given a young earth interpretation of the early chapters of Genesis, we have no reason to reject the idea that Noah brought dinosaurs onto the ark.