Someone mentioned up-thread a bit, that the term "dinosaur" didn't exist until the 19th century. I strongly suspect that when the bible was being written, they had evidence of large creatures unlike anything that they were familiar with. They would have come upon skeletal remains of these huge animals in preparing fields for planting, and in the absence of LIVE ones to study or compare the remains to, they simply made assumptions about what these creature were like, or could do. It's not difficult to imagine people drawing some incorrect conclusions; thus dragons, which we later understood to be dinosaurs. If they found a pterodactyl, then obviously dragons could fly... and of course they exist, because one of them died in Ebenezer's field just down the way, haven't you seen it?