127-million-year-old baby bird fossil sheds light on avian evolution

Scientists have discovered a tiny fossil of a prehistoric baby bird, which can help them understand how early avians came into the world in the age of dinosaurs.
The fossil, which dates back to the Mesozoic Era (250-65 million years ago), is a chick from a group of prehistoric birds called Enantiornithes, according to researchers at the University of Manchester in the UK.
Made up of a nearly complete skeleton, the specimen is amongst the smallest known Mesozoic avian fossils ever discovered.
It measures less than five centimetres - smaller than the little finger on an average human hand - and would have weighed just three ounces when it was alive.

What makes this fossil so important and unique is the fact it died not long after its birth, researchers said.
This is a critical stage in a bird's skeletal formation. That means this bird's extremely short life has given researchers a rare chance to analyse the species' bone structure and development.

"The evolutionary diversification of birds has resulted in a wide range of hatchling developmental strategies and important differences in their growth rates," said Fabien Knoll from the University of Manchester.
"By analysing bone development we can look at a whole host of evolutionary traits," said Knoll, lead author of the study.

With the fossil being so small the team used synchrotron radiation to picture the tiny specimen at a 'submicron' level, observing the bones' microstructures in extreme detail.
The researchers found the baby bird's sternum (breastplate bone) was still largely made of cartilage and had not yet developed into hard, solid bone when it died, meaning it would not have been able to fly.
The patterns of ossification observed in this and the other few very young enantiornithine birds known to date also suggest that the developmental strategies of this particular group of ancient avians may have been more diverse than previously thought.

However, the team said that its lack of bone development does not necessarily mean the hatchling was over reliant on its parents for care and feeding, a trait known as being "altricial."
"This new discovery, together with others from around the world, allows us to peek into the world of ancient birds that lived during the age of dinosaurs," said Luis Chiappe from the LA Museum of Natural History in the US.
"It is amazing to realise how many of the features we see among living birds had already been developed more than 100 million years ago," Chiappe said.