A bird fossil with unusually long fingers discovered 99 million years ago

The researchers discovered a bird's foot dating from 99 million years ago and whose third toe was hyper-stretched. This is the first time that such a foot structure is observed in birds, whether they are extinct or alive.

The study, published in the journal Current Biology, suggests that this bird might have used his toes to extract food from a tree trunk.

"I was very surprised to see amber, which shows that ancient birds were much more diverse than we thought, and they have evolved in many ways to adapt to their environment," he said. said Lida Xing, first author.

To study the fossil Cretaceous period, Mr. Xing and his colleagues scanned amber using a micro-CT and created a 3D reconstruction of the foot. They found that the third toe of the bird, measuring 9.8 millimeters, was 41% longer than the second toe and 20% longer than its tarsometatosis, a bone located in the lower part of the birds' feet. The team compared the ratios with those of 20 other extinct birds of the same era and 62 live birds. No bird has a foot that looks like this one.

The researchers named him Elektorornis chenguangi. Elektorornis means "amber bird", and it belongs to a group of extinct birds called Enantiornithes, the most abundant type of bird known from the Mesozoic era. Enantiornithines are thought to have died out during the Cretaceous-Paleogene extinction event about 66 million years ago, as were dinosaurs. They do not have live descendants.

Based on the fossil record, the team felt that the Elektorornis was smaller than a sparrow and he was arboreal, which meant that he spent most of his time in the trees rather than on the ground or in the water.

"The elongated toes are what we see commonly in arboreal animals because they have to be able to grab those branches and wrap around them." But this extreme length difference, to our knowledge, has never been seen before, "said co-author Jingmai O. Connor.

The amber in which the foot was found, measuring 3.5 cm long and weighing 5.5 grams, was discovered around 2014 in the Hukawng Valley in Myanmar.

In the Mesozoic era, the valley was full of trees producing resin, a sticky substance that flowed from the bark of trees. Plants and small animals, such as geckos and spiders, are often trapped in resin and fossilize with amber after millions of years. Scientists have discovered many extinct animals, including the oldest known bee and a feathered dinosaur tail, in the amber of this valley.

Mr. Xing got the amber from a local amber trader, who did not know which animal belonged to this strange foot.

"Some traders thought it was a lizard foot because the lizards had long toes.Although I've never seen bird claw as similar, I know that it 's a lizard foot because lizards had long toes. is a bird.As most birds, this foot has four toes, while lizards five, "said Mr. Xing.

It is unclear why the amber bird has evolved so unusually. The only known animal with disproportionately long numbers is the aye-aye. The aye-aye is a lemur that uses its long, medium-sized finger to catch larvae and insects in tree trunks for food. Therefore, the researchers suggest Elektorornis could have used his toe for the same purpose.

"It's the best estimate we can have.No bird of similar morphology could be considered a modern analogue for this fossil bird.Many old birds were probably doing things completely different from those of the living birds This fossil exposes a niche that these early risers experienced as they evolved, "said Jingmai O. Connor.

The team hopes to be able to extract proteins and pigments from some feathers exposed on the surface of amber. Mr. Xing said that this data could help them better understand the bird's adaptation to the environment, for example whether or not he had a camouflaged plumage.

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