A 99-million-year-old bird with a toe longer than its legs has been discovered preserved in amber.
The tiny-winged creature had an unusually large digit on each foot, which scientists suggest was used to hook grubs out of tree trunks.
This is the first time such a structure has been seen in birds, either extinct or living, researchers said.
“I was very surprised when I saw the amber,” says first author Lida Xing at China University of Geosciences in Beijing.
“It shows that ancient birds were way more diverse than we thought.
“They had evolved many different features to adapt to their environments.”
The study, published in the journal Current Biology found the bird’s third toe, measuring 9.8 millimetres, is 41% longer than its second toe and 20% than its tarsometatarsus, which is a bone in the lower legs of birds.
Based on the fossil, the team estimates the bird, which they named Elektorornis, was smaller than a sparrow, and spent most of its time in trees.
Co-author Jingmai O’Connor at the Chinese Academy of Sciences, said: “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.”
The amber the foot was found in, measuring 3.5 centimetres long and weighing 5.5 grams, was discovered around 2014 in the Hukawng Valley of Burma.
During the area was full of trees that produced a gooey resin that oozed out of the tree bark.
Small animals like geckos and spiders, and plants, often get trapped in the resin and become fossilised in the amber after millions of years.
The specimen was obtained from a local trader who had no idea what animal the foot belonged to.
Some traders thought it was a lizard’s foot because they tend to have long toes, the scientists said.
However, they explain that like most birds, the foot had four toes, while lizards have five.
The only known animal with disproportionately long digits is the aye-aye – a lemur that uses its long middle fingers to fish larvae and insects out of tree trunks for food.