Tyrannosaurus head on bird body

Today it is widely accepted that birds are descended from dinosaurs. It is also accepted that this transition encompasses some of the most spectacular transformations in the history of evolution from the morphological, functional and ecological point of view, transformations that finally gave rise to the characteristic general body structure of birds.

However, very little is known about the details of this evolutionary leap. Now, a new 120-million-year-old bird fossil from China adds to the mystery by revealing a dinosaur-like skull on a bird-like body. Furthermore, the fossil specimen, of the species that has been named Cratonavis zhui, retains a strikingly elongated scapula and first metatarsal, making it stand out from all other birds, including fossil ones.

The study was carried out by paleontologists from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences.

The Cratonavis sits between the more reptile-like, long-tailed Archeopteryx and the Ornithothoraces (which had already evolved many modern avian traits) on the bird evolutionary family tree.

To study the fossil skull, Zhiheng Li, Min Wang and their colleagues first used high-resolution computed tomography. They then digitally extracted the bones from its rocky tomb and reconstructed the original shape of the skull, allowing them to deduce the functions it was capable of.

Reconstruction of the shape of the Cratonavis zhui. (Image: Chuang Zhao)

The results show that the Cratonavis skull is morphologically almost identical to that of dinosaurs such as Tyrannosaurus rex, rather than resembling a bird.

The study is titled “Decoupling the skull and skeleton in a Cretaceous bird with unique appendicular morphologies”. And it has been published in the academic journal Nature Ecology & Evolution. (Font: NCYT by Amazings)