An ancient bird that lived 99 million years ago had freaky third toes that were even longer than its lower legs.
Researchers discovered the bird foot that had a ‘hyper-elongated’ third toe preserved in amber that was found in Myanmar around 2014.
Based on their scans and analysis of the foot, they suggest that the bird — which was smaller than a sparrow — may have used its toes to hook food out of tree trunks.
This find represents the first time that such a bizarre foot structure has been observed in any bird, either extinct or living.
Palaeontologist Lida Xing of the China University of Geosciences in Beijing and colleagues examined the bird by scanning the amber and creating a three-dimensional reconstruction of the fossil creature’s foot.
‘I was very surprised when I saw the amber,’ Professor Xing said.
‘It shows that ancient birds were way more diverse than we thought. They had evolved many different features to adapt to their environments.’
The researchers found that the bird’s third toe — which measured at 0.38 inches (9.8 millimetres) — is 41 per cent longer than its second toe.
The freakish digit is even 20 per cent longer than the bird’s lower leg bone, the so-called tarsometatarsus.
The team compared these ratios with those of 62 living birds and 20 other extinct birds from the same era.
They found that none of these birds have a foot that resembles this one.
Researchers have named the bird Elektorornis chenguangi, with the first part of its moniker meaning ‘amber bird’
Elektorornis belongs to an extinct group of birds called the Enantiornithes, which are the most abundant type of bird known from the Mesozoic era.
Experts believe that Enantiornithines all went extinct during the so-called Cretaceous–Paleogene extinction event around 66 million years ago which is famous for killing off the dinosaurs.
The Enantiornithines have no living descendants.
Based on their analysis of the fossil, the researchers estimate that Elektorornis was smaller than a sparrow and it lived arboreally — meaning that it spent most of its time in trees, as opposed to on the ground or in water.
‘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,’ said paper co-author and palaeontologist Jingmai O’Connor of the Chinese Academy of Sciences.
‘But this extreme difference in toe lengths, as far as we know, has never been seen before.’
The amber the foot was preserved in — which is around 1.4 inches (3.5 centimetres) long and weighs 5.5 grams — was found in Myanmar’s Hukawng Valley around 2014.
During the Mesozoic era, the valley was full of trees that produced resin — the gooey substance that oozes out of tree bark and can eventually turn into amber.
Plants and small animals — geckos and spiders, for example — often get trapped in resin and become fossilised within the amber, preserving them for millions of years.
Scientists have discovered many extinct animals in amber from this valley, including the oldest-known bee and a feathered dinosaur tail.
Professor Xing obtained the amber containing Elektorornis from a local trader, who did not know which animal the foot belonged to.
‘Some traders thought it’s a lizard foot, because lizards tend to have long toes,’ said Professor 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.’
The only other known animal with disproportionately long digits is the aye-aye — a lemur which uses its long middle fingers to fish larvae and insects out of tree trunks.
Researchers think that Elektorornis might have used its toe for a similar purpose.
‘This is the best guess we have. There is no bird with a similar morphology that could be considered a modern analogue for this fossil bird,’ said Dr O’Connor.
‘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.’
With their initial study complete, the research team hope to extract proteins and pigments from some of the birds’ feathers which are exposed at the amber’s surface.
Analysing these chemicals could help the researchers better understand the bird’s other adaptations to its environment, such as whether it had plumage that camouflaged it, Professor Xing said.
The full findings of the study were published in the journal Current Biology.