A tiny fossil of a prehistoric baby bird is helping scientists understand how early birds evolved 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. (Featured image is an artist impression of Enantiornithes by artist Raúl Martín)

Smallest Mesozoic Avian Fossil

Made up of a nearly complete skeleton, the specimen is amongst the smallest known Mesozoic avian fossils ever discovered.

It measures less than five centimeters – smaller than the little finger on an average human hand – and would have weighed just 0.3 ounces when it was alive.

What makes this fossil so important and unique is the fact it died not long after its birth.

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 analyze the species’ bone structure and development.

Ossification Holds the Key

Studying and analyzing ossification – the process of bone development – can explain a lot about a young bird’s life the researchers say.

It can help them understand everything from whether it could fly or if it needed to stay with its parents after hatching or could survive on its own.

Dr. Fabien Knoll in lab analyzing bone development of the baby bird fossil. Photo credit: The University of Manchester

Dr. Fabien Knoll in lab analyzing bone development of the baby bird fossil. Photo credit: The University of Manchester

“The evolutionary diversification of birds has resulted in a wide range of hatchling developmental strategies and important differences in their growth rates. By analyzing bone development we can look at a whole host of evolutionary traits,” says Fabien Knoll, the lead author of the study from The University of Manchester’s Interdisciplinary Centre for Ancient Life (ICAL), School of Earth and Environmental Sciences, and the ARAID — Dinopolis in Spain.

New Technologies Offer Scientists Glimpse Into Ancient Birds

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.

“New technologies are offering palaeontologists unprecedented capacities to investigate provocative fossils. Here we made the most of state-of-the-art facilities worldwide including three different synchrotrons in France, the UK, and the United States,” says Dr. Knoll.

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 wouldn’t 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.

Phosphorous mapping and photo of fossil. Photo credit: The University of Manchester

Phosphorous mapping and photo of fossil. Photo credit: The University of Manchester

However, the team says that its lack of bone development doesn’t necessarily mean the hatchling was over-reliant on its parents for care and feeding, a trait known as being ‘altricial’.

Modern-day species like love birds are highly dependent on their parents when born. Others, like chickens, are highly independent, which is known as ‘precocial.’.

Although, this is not a black-and-white issue, but rather a spectrum, hence the difficulty in clarifying the developmental strategies of long gone bird species.

Age of Dinosaurs

Luis Chiappe, from the LA Museum of Natural History and study’s co-author, adds, “This 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. It is amazing to realize how many of the features we see among living birds had already been developed more than 100 million years ago.”
Read the full abstract, ‘A diminutive perinate European Enantiornithes reveals an asynchronous ossification pattern in early birds’ published in Nature Communications, 2018 here.