When sportsmen use rackets or bats, their best bet is to hit a ball on the “sweet spot”, the point where various forces balance out to deliver powerful blows with only very small forces on the wielder’s wrist. Engineers have the right tools and models to work out where this spot lies on their instruments. Now, palaeontologists have used the same techniques to study biological hammers that adorn the tails of giant prehistoric armadillos called glyptodonts.

At first glance, glyptodonts have little in common with the likes of Andy Murray and Roger Federer. These armoured beasts lived in the Americas several million years ago and the largest of them weighed up to two tons. Much like their modern armadillo relatives,