Some dinosaurs had club-like tails that they smacked into foes, and now researchers have discovered that the wings of an extinct Jamaican bird evolved into similar structures that the bird would use to clobber rivals during fights.
The bird, Xenicibis xympithecus, is the first known animal that had limbs modified to serve as a club/flail, according to the authors of the study. The paper is published in the latest Proceedings of the Royal Society B.
Before the flightless bird went extinct 10,000 or fewer years ago, it must have engaged in some fierce fighting at its island nation home. Unearthed fossilized remains retain signs of traumatic injuries sustained from delivering or receiving blows.
"I would guess that they would try to grab each other using the beak and then just proceed to pound each other using the wings," co-author Nicholas Longrich told Discovery News.
Co-author Storrs Olson of the Smithsonian Institution’s National Museum of Natural History added that such fighting would have likely applied to aggression between males, although females had the wing "weapons" too, perhaps to beat off snakes, monkeys and other potential predators that might have gone after their young.
Longrich, a post doctoral associate in the Department of Geology and Geophysics at Yale University, and Olson made the determination after analyzing the remains of the bird, which was a relatively large long-billed, long-legged wading ibis. They immediately noticed the bird’s "bizarre" wings.
"The arm is long and spindly, and the hand bones are enlarged, curved and expanded so that the hand looks like a banana," Longrich said.
He and Olson believe the wings functioned like handled clubs and flails, with the arms being the "handles" of the weapons, increasing the angular velocity of the weighted "club" at the end. The bird could then swing its wings, delivering sharp blows whenever the enlarged hand bones struck an opponent.
The researchers suspect many fights had to do with staking out home turf.
"There were a lot of birds fighting over the same territories," Longrich explained. "The best fighters -- the ones with the best weapons -- were able to secure a good territory and reproduce."
A number of birds use their wings as weapons. The scientists note that some birds, including screamers, certain jacanas, the spur-winged goose, the torrent duck and nine species of lapwing, employ sharp spurs.
Other birds, such as steamer ducks, sheathbills, stone curlews and swans, bear a bony knob on their wings. Two jacanas, Actophilornis and Irediparra, even have triangular blades on their wings. But no bird, and no other vertebrate living or extinct, possessed limbs modified to serve as a jointed club or flail that could be swung, according to the scientists.
Richard Prum, chair of Yale’s Department of Ecology & Evolutionary Biology, told Discovery News that the new findings are "very surprising and exciting."
"The authors make a good argument for a novel combat function for the flightless forelimbs of this weaponized ibis," Prum said. "Clearly there is much more to learn about avian diversity."
Helen James, curator of birds at the National Museum of Natural History, believes "the authors are correct that the wing had evolved to serve as a specialized weapon."
"I can just imagine the rapid-fire blows that these ibises could deliver with their flail-like wings," she added.