Two of the following hypotheses were something scientists actually used to think about dinos, and one is the by-product of my fevered Friday imagination. See if you can guess which is which: 1) The Stegosaurus had a brain in its butt, 2) the Loch Ness Monster exists, and is a particularly long-lived Plesiosaur, and 3) the Pterodactyl was actually flightless and used its wings to hide from predators, much in the manner of an ostrich sticking its head in the ground.