Xenicibis is a large, extinct, flightless ibis. It was discovered by Storrs Olson from the Smithsonian Institution, who found some partial remains in a Jamaican cave in 1977. When Olson eventually saw the bird’s wing bones, he was baffled. They were so “utterly strange” that he thought the animal must have been suffering from some inexplicable disease.

Since then, Olson has found more remains including an almost complete skeleton. Now, he and his partner Nicholas Longrich from Yale University, have a very different view of the wing. They think it was a club. Weapons like clubs and bats have large weighted ends to deliver heavy impacts, and long handles to increase the speed of the swing. That’s exactly what you see in Xenicibis’s wing.