Why does a uromastyx always look happy?

That's a pretty hilarious question, and anyone who has ever owned or been around them will know exactly what you're talking about. You aren't the only one that things their faces always look happy due to the way their mouths are shaped. Baby bearded dragons have that same sort of smile on their faces, and they look cute and happy as well.

I read a study done at the University of Leeds in the United Kingdom that included study of Uromastyx and its predecessors, and the shape of their head seems to have evolved that way so it can not put so much strain on the rest of its head while it is eating or fighting. The exact words were "Development of a lower temporal bar apparently provided additional support for an immobile quadrate that could become highly stressed during forceful biting. "