A 115-million-year-old fossilized bird with a pair of long, ribbon-like tail feathers is the oldest bird ever found in Brazil. It was about the size of a hummingbird, and it likely boasted bright colors, according to findings published in Nature Communications this week.
Most of what we know about the early evolution of bird feathers comes from Cretaceous bird fossils uncovered in northeast China. Ribbon-like feathers – glamorous features that don’t exist in living birds today – are also known as rachis-dominated feathers. The rachis (or the shaft) makes up at least the first half of the feather. All of these sorts of fossil feathers were previously recovered from two-dimensional slabs, so we don’t know very much about their shape when the birds were alive.
But now, a team led by Ismar de Souza Carvalho from Universidade Federal do Rio de Janeiro analyzed a three-dimensional bird fossil from the Araripe Basin within the Pedra Branca Mine of northeast Brazil. The body itself is about 6 centimeters long, and it’s the most complete avian specimen to date from the Early Cretaceous period in Gondwana, the more southerly supercontinent.
Based on the fossil’s large eyes and certain aspects of its bone development – such as the undeveloped ends of the long bones and the lack of fusion in the foot bones – the bird was likely a juvenile. Despite being young, its 8-centimeter-long tail plumage resembles the feathering of modern adult birds.
The tail feathers have an elliptical shaft, and at the base of the rachis, the researchers found a row of five round spots -- likely the remnants of an ornamental color pattern. The spots are distributed in a symmetrical paired line along both feathers, and because they all have a similar size, shape, and color, the team believe that they’re not simply artifacts of the fossilization process. These jazzy tail feathers could have been used for sexual display, species recognition, or visual communication. Because the feathers aren’t aerodynamically optimized, they probably didn’t play much of a role in balance or flight.
The small, toothy bird belongs to an extinct group known as the Enantiornithes, but the team haven’t determined the genus and species just yet. "We are still comparing it with some birds that came from other parts of Gondwana to decide, exactly, the name that it will have," de Souza Carvalho tells Live Science.
Until now, ancient birds with ribbon-like tail feathers have only been reported in China. This new fossil, the first of its kind to be found in South America, significantly widens the distribution of birds with this feather type.
Images: Deverson Pepi (top), Ismar de Souza Carvalho (middle)