This is What Millions of Years of Head-Butting Will Do

This animal is Moschops capensis, an ancestor of mammals that lived 250 million years ago. It has a particularly thick skull, according to the fossil evidence, which made it look really weird. What we are learning about Moschops is thanks to some ultra high-tech research in France, where a combined CT and Synchrotron scanner was used to analyze Moschops skull fossils to see how really thick they were, and where the soft tissue would have fit inside. 

With a body weight reaching up to one or two tons and a brain the size of a chicken egg, Moschops‘s brain was probably one of the smallest among its contemporaneous species. However, small brain size is not an issue when you are the largest animal of your time. Unlike mammals and humans, the ability of the Moschops to survive and reproduce was not a matter of how smart it was, but how strong it was, particularly when it came to fierce head-to-head combat.
Their anatomy shows that male Moschops were ramming into each other like giant, overweight goats using their skulls as a weapon.
The very fact that Moschops was practising headbutting testifies to a certain level of social organisation, which is often associated with hierarchical ranking in modern species. So, despite its small brain, the Moschops wasn’t stupid.

Okay, so they weren't stupid. But thanks to natural selection, they were rather ugly. Read more about the new research into Moschops and their skulls at the Conversation.