Bizarre Dinosaur-bird Hybrid Soared the Skies of China Over 120 Million Years Ago, Fossil Analysis Revealed

A fossil analysis revealed that a bizarre dinosaur-bird hybrid soared over China about 120 million years ago, during the Cretaceous period. The fossil has a dinosaur-like head with a bird-like body.

MailOnline reported that researchers named the newly-discovered body print fossil Cratonavis zhui, which was found during excavations in northern China, in a region where prints of feathered dinosaurs and early birds were unearthed before. Paleontologists noted that the strange discovery may offer important insights into the evolution of modern birds.

Reconstructing the Dinosaur-Bird Hybrid Fossil

The scientists, led by Chinese Academy of Sciences (CAS) paleontologist Zhou Zhonghe, began their research of the ancient skull with high-resolution computed tomography (CT) scanning.

According to Science Alert, the team rebuilt the shape and function of the skull as it was throughout the bird's life using digital copies of the calcified bones. The findings suggest that the Cratonavis skull is almost identical to those of dinosaurs such as Tyrannosaurus rex, rather than a bird's.

CAS paleontologist Zhiheng Li wrote in their study that the primitive cranial features show that most Cretaceous birds, like Cratonavis, were unable to move their upper bill independently because of their braincase and lower jaw. This functional innovation was passed down to generations of birds, which contribute to their enormous ecological diversity.

The uncommon pairing of an akinetic dinosaur skull and a bird skeleton adds to prior research on the role of evolutionary mosaicism in the early diversification of birds.

Cratonavis is located between the long-tailed Archaeopteryx, which was more like a reptile, and the Ornithothoraces, which had already evolved many of the characteristics of modern birds.

Dinosaurs Developed Short Metatarsals After Evolving Into Birds

The Cratonavis fossil also possesses a very large scapula and first metatarsal or foot bone, which are characteristics that are seldom observed in other dino-ancestors birds and are entirely absent in contemporary birds. Dr. Min Wang said that the scapula of Cratonavis zhui is functionally vital to avian flight as it is responsible for stability and flexibility.

As birds evolved, evolutionary patterns reveal that the length of the first metatarsal decreased, Sci-News reported. Dr. Wang noted that there are changes in the scapula as well across the theropod-bird transition. These differences represent morphological experimentation early in bird diversification.

More so, the fossil analysis showed that the first metatarsal was subjected to selection when dinosaurs were evolving into birds that favored the shorter bone. They lost their evolutionary lability once they reached the optimal size, which is less than a quarter of the length of the second metatarsal.

However, Dr. Thomas Stidham explained that enhanced evolutionary lability was seen among Mesozoic birds and dinosaur relatives, which may have stemmed from competing demands linked with their direct use of the hallux in movement and eating. The elongated hallux in Cratonavis zhui likely stems from selection for raptorial behavior.

Dr. Zhonghe noted that changes in scapula and metatarsals across the theropod tree show clade-specific evolutionary lability that resulted from the interplay among development, natural selection, and ecological opportunity.

The team published the findings of their study, titled "Decoupling the Skull and Skeleton in a Cretaceous Bird With Unique Appendicular Morphologies," in the journal Nature Ecology & Evolution.

Check out more news and information on Paleontology in Science Times.