Take, for instance, the carnotaurus they showed doing a mating display. He was the guy with the fancy, little blue underarms. What makes the paleontologists think those arms were for a mating display? Well, for a mini lesson on evolution, I can tell you that an organism does not evolve to have something as complicated as ball and socket joints without reason. You don’t waste vital energy on something like that unless it’s important, especially for something that would otherwise be considered vestigial at best. Arms like that are much too small to assist in fighting or hunting. Which means it must assist in the, uh, “passing along of genes.” From there you can follow the line of logic that paleontologists would have. Animals today have mating displays, especially reptiles and birds (AKA dinosaur descendants), so why wouldn’t dinosaurs have similar displays? It makes sense, evolutionarily speaking. So, if you’re looking for answers to questions like that, you’ve come to the right place. I’ve done the leg work and collected some natural history and paleontology books that will fill in the blanks and teach you more about how the world once was. If this has just started to scratch your inner child’s itch for dinosaur books or you have an actual child yearning for the paleontological, I recommend you check out this list of good dinosaur books for preschoolers, some books about dinosaurs in general, or if general natural history is more your thing, you can check out some recent nonfiction books on that very topic.