Bird With Toes Longer Than Its Lower Legs Discovered in 99 Million-year-old Amber

Scientists who studied bones trapped in amber for millennia say they have discovered a bird which lived 99 million years ago that had toes longer than its lower legs.

The bird's foot, including a third toe measuring 9.8 millimeters, was found in amber in the Angbamo area of the Hukawng Valley of northern Myanmar in 2014, and dates back to the middle Cretaceous period.

These origins lead the team to name the bird, which is smaller than the average modern-day sparrow, as Elektorornis chenguangi, or "amber bird."

The Elektorornis chenguangi is a member of the Enantiornithes family of birds. Wiped out in the Cretaceous-Paleogene extinction event around 66 million years ago, they were the most common birds of the Mesozoic era.

Lida Xing at China University of Geosciences, the first author of the study published in the journal Current Biology, acquired the 3.5 centimeter long block of amber from a local trader, who thought it contained a lizard's foot.

amber, fossil, bird foot,
This photograph shows a nearly 100-million-year-old bird foot featuring a very long toe preserved in amber. The specimen also contains the bird's left wing tip. Lida Xing

"Although I've never seen a bird claw that looks like this before, I know it's a bird. Like most birds, this foot has four toes, while lizards have five," said Xing in a statement.

Using the scientific term for tree-dwelling birds, Jingmai O'Connor at the Chinese Academy of Sciences, co-author of the study, commented in a statement: "Elongated toes are something you commonly see in arboreal animals because they need to be able to grip these branches and wrap their toes around them. But this extreme difference in toe lengths, as far as we know, has never been seen before."

After scanning the amber, the team created a 3D computerized model of the foot.

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A 3D reconstruction of the foot skeleton found in amber. Lida Xing / Current Biology

The 9.8 millimeter toe was 41 percent longer than its second, and 20 percent longer than its lower leg bone, or tarsometatarsus. To confirm the bird's toe was unique, the scientists tried to match it with the bones of 20 extinct birds which lived during the same period, as well as 62 living birds.

Xing said in a statement: "It shows that ancient birds were way more diverse than we thought. They had evolved many different features to adapt to their environments."

The authors of the paper think this is the first time a bird with this type of foot shape has been found. They believe the bird probably mostly lived in the trees, and might have used its huge toes to pick food out of bark, similarly to the aye-aye lemur.

"This is the best guess we have," O'Connor says. "There is no bird with a similar morphology that could be considered a modern analog for this fossil bird. A lot of ancient birds were probably doing completely different things than living birds. This fossil exposes a different ecological niche that these early birds were experimenting as they evolved."

Juan Daza, a herpetologist and assistant professor in reptile morphology at Sam Houston State University who was not involved in the work told Newsweek: "This bird fossil foot is unique in terms of the proportions of the toes.

"Long toes like these are present today in modern birds such as the aquatic Jacanas (wading birds), but contrary to the fossil, the second and third toes of birds like Jacanas are equally elongated, resulting in a more symmetrical foot than in Elektorornis chenguangi where the third toe is considerably longer. The current study reports a new kind of enantiornithe ecomorph that might have a distinctive foraging mode."