When it was first revealed that feathers from ancient birds were able to survive fossilization, it shook the scientific world. Previously, it was only thought that hard tissue could survive the process of being turned into fossils, but slowly increasing evidence was gathered that showed soft tissue such as the feathers of birds – and dinosaurs – can, in fact, survive for tens of millions of years. But that is not the only way that soft tissue can survive.
A new paper, published in Nature Communications, describes the astonishing discovery of two bird wings preserved in amber that date to around 99 million years old. The finding is vastly important: Previous evidence of fossil wings are usually preserved in only two dimensions due to the nature of fossil preservation. The odd feather has been found before in amber, but these are disassociated from the soft tissue that they once were embedded in, but not in these new findings.
The discoveries come out of the Burmese amber deposits which, dating to the mid-Cretaceous, have been found to contain an astonishing array of insects, plants, and animals perfectly preserved in the fossilized tree resin. From entire lizards frozen in time, the eternal priapism of a harvestman, or the evidence of the oldest ant societies yet discovered, the deposits keep revealing more and more outstanding discoveries. This latest find adds yet another.
The fossils are only partial wings, but from them the researchers are able to learn a lot about the ancient birds, and their morphology. They have been able to see the very first examples of hair follicles and feather arrangements from the Cretaceous, and by using X-ray micro-CT scanning, were able to examine the structure and arrangement of the bones in the fragments of wings preserved. The barbs on the feathers show that they had interlocking feathers, and therefore suggest that the birds had powered flight, a consistent finding with other traditional fossils.
The size of the wings strongly suggests that they belonged to juvenile animals of a now extinct group of birds known as Enantiornithes. Coupled with the well-developed feathers, however, the researchers suspect that the young chicks were what is known as “precocial”, meaning that the young hatch from the eggs and are relatively mature and mobile, as opposed to the blind naked chicks in nests, which are “altricial”.
The amazing fossil wings show that most of the feather types found in modern birds were already present in those flying around the Cretaceous forests some 100 million years ago, even displaying similar pigmentation, arrangement on the wing, and microstructure.
Top image in text: Reconstruction of birds in real life. Chung-tat Cheung
Bottom image: One of the fossils. RSM/ R.C. McKellar