There once was a little bird, smaller than a sparrow, that lived about 99 million years ago. And it had a freakishly long toe.
Researchers found the ancient bird’s right leg and foot preserved in a chunk of amber. Its third digit is 9.8 millimeters long, about 41 percent longer than its second-longest digit — and 20 percent longer than its entire lower leg. This foot morphology is unique among any known bird species, whether modern or Mesozoic, the team reports online July 11 in Current Biology. Although it’s not clear what purpose the extra-long toe served, the digit may have helped the bird find food in hard-to-reach places, such as through a hole in a tree.
The team, led by paleontologist and frequent amber-fossil finder Lida Xing of the China University of Geosciences in Beijing, compared the toe size ratios of the fossilized bird with those of 20 other birds that lived during Mesozoic, the era that spans between 252 million and 66 million years ago, as well as with toe size ratios of 62 living species. Although some modern tree-dwelling birds do have elongated third digits, none of the other birds living or extinct have quite such a dramatic difference in toe sizes, the team found.
Determining the bird to be a new species, the team named it Elektorornis chenguangi — using the prefix elektor, meaning amber in Greek, and suffix ornis, meaning bird; and with a nod to Chen Guang, the curator at the Hupoge Amber Museum in Tengchong City, China.
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E. chenguangi was a member of a group of toothed, clawed birds called enantiornithines that died out along with nonavian dinosaurs about 66 million years ago. Like most enantiornithines, the tiny E. chenguangi was probably a tree-dweller, and that lengthy digit may have helped the bird to grasp on to tree branches and limbs — in addition to possibly giving it a leg up in feeling around for food.
Editor’s note: The second caption in this story was updated July 17, 2019, to correct the comparison between E. chenguangi‘s longest and second-longest digits. The third digit is 41 percent longer than the second-longest digit, not twice as long.