Quirks & Quarks

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

This tiny bird discovered in Spain, preserves remarkable details of bone structure
This bird lived 127 million years ago (Raul Martin)

The fossil

Five years ago, paleontologists found a baby bird fossil in the Las Hoyas deposit in Spain, which is a site famous for remarkable fossil preservation. The tiny fossil measured less than five centimetres. It was determined to be 127 million years old, which places it in the Mesozoic Era. The fossil comprises a nearly complete skeleton which makes it among the smallest known avian fossils from that era ever discovered. It is from a group of prehistoric birds called Enantiornithes.     

The bird

By looking closely at bone structure and development, researchers including Dr. William Sellers, a professor in the School of Earth and Environmental Sciences at the University of Manchester in England, can tell that this bird did not live long after its birth. They also determined that it was old enough to no longer be in the care of its parents, yet young enough to be still going through bone development. For example, the sternum was soft cartilage instead of hard bone.  The indicates that the sternum was unlikely able to support the muscles required for flight, yet this species likely could fly. The pristine condition of the fossil suggests that this bird died suddenly and was quickly covered over. 

What it reveals

The patterns of this bird's bone structure and development - called ossification - suggest a great diversity among ancient avians than previously thought. But scientists were surprised to see that many of those growth strategies seen in this fossil from 127 million years ago are still seen in birds today. It is difficulty for scientists to determine this birds species because there aren't any other fossils for comparison. They can say for sure that it did not give rise to any species known today.