Imagine having a toe as long as your shin. That’s essentially what researchers have found in a bird foot trapped in amber for nearly 100 million years. The appendage features an extremely long third toe never before seen in birds.
Amber dealers suspected the fossil foot, originally found in the Hukawng Valley of Myanmar in 2014, belonged to a lizard, which are known for their long toes. But lizards have five toes, suggesting the sample belonged to a bird instead.
In the new study, researchers used detailed x-ray scans to create a 3D model of the foot. They then compared it with the feet of more than 80 modern and ancient birds. The fossil’s third toe, which measures nearly 10 millimeters, is 20% longer than its lower leg and more than 40% longer than its second toe, the team reports today in Current Biology. No other bird—living or extinct—sports such an appendage.
It’s unclear what the bird—which the researchers have christened Elektorornis chenguangi (seen in this artist’s conception)—used the toe for. (Elektorornis means “amber bird,” and the second half of the name is a nod to the discoverer of the fossil, Chen Guang.) Lengthy toes are a common feature of tree-dwelling animals like squirrels and monkeys because they improve branch grip. Researchers speculate that the unusual adaptation may have been used to dig food out of tree trunks. Whatever the reason, it wasn’t a feature that caught on. Elektorornis vanished with the dinosaurs 66 million years ago, leaving no modern descendants.