Ancient bird with toe longer than its leg found fossilised in amber

James Marshall
Июля 12, 2019

A 99-million-year-old bird with a toe longer than its legs has been discovered preserved in amber.

Enantiornithes were wiped out along with the non-avian dinosaurs, while Neornithes went on to become the diverse group of birds - from ostriches to penguins, eagles to hummingbirds - that now inhabits our planet.

"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", says co-author Jingmai O'Connor at the Chinese Academy of Sciences.

The soft tissue, found on the bird's foot, is also without parallel.

The "amber bird" apparently belongs to a group of extinct creatures called Enantiornithes-once abundant during the Mesozoic era. But that abruptly changed when a huge asteroid hit Earth 66 million years ago. The appendage features an extremely long third toe never before seen in birds.

O'Connor said the fossil illustrates the "weird" lifestyle and anatomy of early birds, with the foot only the latest in a flurry of ancient animal remains found in Myanmar amber.

The bird's leg, foot and left wing tip were trapped in amber millions of years ago. Scientists have discovered many extinct animals, including the oldest known bee and a feathered dinosaur tail, in amber from this valley.

The fossil was recovered in 2014, and at first, it was thought it might have belonged to a lizard, but further tests showed that it was the foot of a bird.

"I was very surprised at the time", Dr Xing told the Times, recalling that the fossil was "undoubtedly the claw of a bird".

"Some traders thought it's a lizard foot, because lizards tend to have long toes", Xing says.

Paleontologists are unsure what goal the extra-long toe served, but it may have helped the cretaceous period bird find food in difficult-to-reach places such as holes in trees.

Scientists remain stumped as to why the amber bird evolved such an unusual feature.

The only known animal with disproportionally long digits, in fact, is the aye-aye, a lemur that uses its fingers not so much for balance, but for foraging in hard-to-reach places, like tree trunks that house juicy larvae and insects. The team believes Elektorornis may have used its toe for the same objective.

"Enantiornithines were good enough to survive and dominate in the Cretaceous but maybe not good enough to make it through the mass extinction", O'Connor said. "There is no bird with a similar morphology that could be considered a modern analog for this fossil bird". Such data could help shine a light on the bird's evolutionary adaptations.

This work is supported by the National Natural Science Foundation of China, the National Geographic Society, USA, the Fundamental Research Funds for the Central Universities, and Natural Sciences and Engineering Research Council of Canada.

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