120-Million-Year-Old Fossil Found in China Has A Bird-Like Body, A Dinosaur-Like Skull

The bizarre bird fossil found in northern China has a skull similar to that of a Tyrannosaurus rex. The fossil in question may contain clues about the evolution of birds.

The fossil was found in northern China, in an area where dinosaur remains and early bird species have been unearthed. Examining the fossil, scientists concluded that they were dealing with a genus from the Early Cretaceous.

The fossil, identified as Cratonavis zhui, was reported on January 2, 2023, via an article published on Nature Ecology & Evolution.1

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Chinese Academy of Sciences / Zhao Chang

The study, led by the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, revealed that the head of the fossil is almost identical to that of dinosaurs. The fossil also supports theories for evolutionary mosaicism in early bird diversification.

What is mosaic evolution?
Mosaic evolution or evolutionary mosaicism refers to evolutionary change occurring without simultaneous changes in some body parts or organs. For example, although the ability to walk on two legs developed in early Homo species, the brain did not develop at the same rate.

Scientists using computer tomography to examine the fossil were able to obtain detailed information in this way.

The fact that the fossil has an elongate scapula and first metatarsal makes it distinct from all known bird species. This means that Cratonavis zhui has a special place in the evolutionary path from dinosaurs to modern birds.

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Chinese Academy of Sciences / Wang Min

Evolution of birds
Birds began to evolve from the theropods, a clade of dinosaurs, during the Jurassic period, some 200 million years ago to 150 million years ago. Many paleontologists regard birds as dinosaurs that survived the Cretaceous-Paleogene extinction event that occurred 66 million years ago.

Paleontologists sit Cratonavis taxonomically between Archeopteryx and Ornithothoraces.

  1. Li, Z., Wang, M., Stidham, T.A. et al. Decoupling the skull and skeleton in a Cretaceous bird with unique appendicular morphologies. Nat Ecol Evol 7, 20–31, 2023[]