Duckbill crests

Certain duckbilled dinosaurs known to every parent who reads dino books out loud these days -- corythosaurus, parasaurolophus -- have elaborate crests on their heads. The dinosaurs' nasal passages wind through these crests. Why? The two main theories have long been 1) to make low-frequency sounds for communication and 2) for smelling. Modeling of duckbill brains now suggests that explanation 1 is correct. The parts of the brain responsible for olfactory processing in these animals were small, so they are unlikely to have relied much on their sense of smell, but they do have very elaborate inner ears that could have processed low-frequency sound.

This may not sound like much to you, but when you have said "nobody really knows what the crests on their heads were for" as many times over the past ten years as I have, this is a pretty big deal.