A bizarre creature that lived in China around 120 million years ago had a dinosaur's head and a bird's body, a study published in Nature Ecology & Evolution revealed.
Researchers at the Chinese Academy of Sciences (CAS) studied the recently discovered complete fossil of the creature named Cratonavis zhui. They found that the chicken-sized hybrid had long shoulder blades and claws, but its large skull was shaped in an almost identical way to that of T-Rex and other meat-eating theropods.
The researchers studied the fossil by using high-resolution computed tomography, or CT scans. This enabled them to digitally manipulate the specimen's bones and reconstruct the original shape of the skull, and even deduce some of its dinosaur-related functions.
According to the study, the team also analysed Cratonavis' shoulder blade and metatarsal, a long bone in the foot that connects the ankle to the toes, in order to understand more about its birdlike body. They confirmed that the creature's skull is morphologically nearly identical to those of dinosaurs, rather than those of standard birds.
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“The primitive cranial features speak to the fact most Cretaceous birds such as Cratonavis could not move their upper bill independently with respect to the braincase and lower jaw, a functional innovation widely distributed among living birds that contribute to their enormous ecological diversity," Li Zhiheng, a lead author of the study, said.
As for the creature's shoulder blade, researchers explained that it was functionally “vital” to avian flight, meaning it helped Cratonavis exhibit strong stability and flexibility while airborne. The new also study showed that the first metatarsal (foot bone) was subjected to selection during the dinosaur-bird transition that favoured a shorter bone. It then lost its evolutionary lability once it reached its optimal size, less than a quarter of the length of the second metatarsal.
The researchers said that the study fills in some of the gaps as to how some dinosaurs evolved into birds. The bizarre creature's unique mix of anatomy is also a sign of how all living things represent increments of change, and the evolution of birds of all feathers occurred simultaneously along a wide variety of divergent paths.
