Scientists: Ancient Bird Evolved 'Nunchuck' Wings
The chicken-sized bird, with a long beak and legs, couldn't fly and had no way to defend itself, aside from with its strong arm-wings. With thick, curved arm bones hinged at the shoulder, the birds are believed to have used their wings not for flight but to fight -- flailing them as a defense mechanism. The bizarre appendage has never been seen in any species before.
"It's the most specialized weaponry of any bird I've ever seen," Nicholas Longrich, of Yale University's Department of Geology and Geophysics, said in a statement excerpted by Scientific American magazine. "The arm is long and spindly, and the hand bones are enlarged, curved and expanded so that the hand looks like a banana."
"I sometimes compare these things to nunchucks, which I guess would make this a ninja bird, although perhaps a better analogy would be a pair of baseball bats -- they were actively swung rather than moving passively like a flail or nunchaku," Longrich told LiveScience.com.
The bird, whose scientific Latin name is Xenicibis xympithecus, was first discovered in the 1970s by experts at the Smithsonian Institution. Now scientists have found new fossils of the birds with broken arms -- injuries they say were probably sustained in fights with predators. Details are published in the Jan. 4 issue of the journal Proceedings of the Royal Society B.
One of the authors, Longrich also told the Discovery Channel that he believes the birds "would try to grab each other using the beak and then just proceed to pound each other using the wings."
Such fighting would have occurred between aggressive males of the same species, but also females, who needed to fend off snakes, monkeys and other predators that might have tried to attack their babies, co-author Storrs Olson, with the Smithsonian's National Museum of Natural History, told Discovery.
The species is believed to have gone extinct in Jamaica as recently as 10,000 years ago. Long before that, it may have had normal wings that allowed it to fly, but its club-like arms likely evolved from those over time.
"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."
Some other birds are also believed to fight with their wings, including swans, who do so to protect their young. Others, including screamers, lapwings and the spur-winged goose, have evolved bony knobs on their arms to increase damage to attackers.
"But among vertebrates, there's no animal of any sort that has anything like a limb modified as a club," Longrich told the BBC.