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, they were clad in large suits of bony armour. Their long tails were similarly protected by bony rings and in some species, they were topped with large clubs, or spiky weapons that resembled medieval morning stars.
Uruguayan scientist Rudemar Ernesto Blanco was set about studying the tail clubs of the most formidable of the glyptodonts, by using the same approaches used to analyse sports tools. The analogy is particularly appropriate for species like Doedicurus, where the rings at the end of the tail were completely fused, meaning that the animal’s rear end was defended by a single metre-long piece of solid bone – a biological hammer, indeed.
When wielding this weapon, whether against a predator or a fellow glyptodont, it would be in the animal’s interest to strike at the sweet spot of its own tail to reduce the forces acting on the part of the tail where the bony tip met the more flexible base. Otherwise, it might have risked severe strain and damage. To find the locations of these spots, Blanco applied sports modelling techniques to the tails of nine species of glyptodonts.