The tiny, finger-sized fossil of an ancient bird that lived around 250 to 65 million years ago is helping researchers gain insight into how early birds originated in the age of dinosaurs.

The Mesozoic Era fossil belonged to a type of prehistoric birds known as Enantiornithes, and it is the smallest discovered Mesozoic avian fossil to date.

The fossil comprises of a nearly intact skeleton, measuring less than 5 centimeters, indicating that the bird was tinier than the pinky finger of an average-sized human hand. The tiny bird would have had a weight of 0.3 ounces during its short lifetime.

A Mesozoic Era Baby Bird Fossil

The baby bird died soon after its birth, which is a crucial stage in the skeletal form of a bird. The short lifespan of the bird has given paleontologists the rare opportunity to study the bone structure and development of the species.

The bone development process could also help the researchers comprehend if it could survive on its own after hatching or had to stay with its parents as well as if it could fly.

"The evolutionary diversification of birds has resulted in a wide range of hatchling developmental strategies and important differences in their growth rates," said study lead author Dr. Fabien Knoll, from the University of Manchester.

Knoll also noted that the analysis of bone development could help scientist look at a variety of evolutionary traits.

Discoveries Made With The Help Of The Fossil

The research team took the help of synchrotron radiation to photograph the tiny fossil at a submicron level, which enabled them to observe the microstructures of the bones in great detail. They discovered that the breastplate bone, called sternum, had still not evolved into a solid, hard bone, which indicated that the bird could still not fly.

The bone development pattern of the fossil also suggested that the strategies of development for enantiornithines were more varied than previously held by researchers.

The paleontologists also added that the lack of bone development seen in the fossil does not always suggest that the bird was not too dependent on its parents for feeding and care.

The coauthor of the study, Luis Chiappe, said that the new discovery, along with other such discoveries from all over the globe, has allowed researchers to glimpse into the era of prehistoric birds that existed during the dinosaur age. He added that it is amazing to see that many of the modern-day bird features had already come into existence over a 100 million years ago.

The study has been published in in the journal Nature Communication on March 5.