The theory that birds are descended from dinosaurs is now widely accepted. This transition is also understood to involve some of the most dramatic morphological, functional and ecological changes that eventually led to the distinctive body structure of birds.
However, paleontologists are still scratching their heads to understand how this spectacular evolutionary event happened, which is why the latest discovery of Chinese Academy of Sciences: A. Kratonvis Zhui.
is about a whole new fossil bird which was found in the Asian country, 120 million years old, Which, Chinese experts say, further complicates the issue by displaying an artificial dinosaur-like skull with a bird-like body.
Furthermore, the experts elaborated through a statement that this fossil specimen It retains a surprisingly elongated scapula and first metatarsal, making it stand out among all other birds, including fossils.
The study, published January 2 in Nature Ecology & Evolution, was conducted by paleontologists from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences.
On the avian evolutionary tree, Cratonavis is located between the more reptile-like long-tailed Archeopteryx and Ornithotaurus (which had already developed many modern bird traits).
The scientists said they first used a high-resolution computed tomography (CT) scan to study the fossilized skull. They then digitally extracted the bones from their rocky tombs and reconstructed the original form and function of the skulls.
the result shows that The skull of Cratonavis is morphologically almost identical to that of dinosaurs such as Tyrannosaurus rex, rather than bird-like. “The primitive cranial features speak to the fact that most Cretaceous birds, such as Cratonavis, could not move their upper beak independently in relation to the braincase and lower jaw, a widely distributed functional innovation among living birds. contributes to its enormous ecological diversity,” said Dr. Li Zhiheng, lead author of the study.
Regarding the alien scapulae and metatarsals in Cratonavis, Dr. Wang Min, lead and corresponding author of this study explained that the scapula is functionally important for avian flight and confers stability and flexibility.
“We trace changes to the scapula through the theropod-bird transition, and believe that the elongated scapula may have increased the mechanical advantage of the muscles for humerus retraction/rotation to compensate for the overall underdeveloped flight mechanism in this primitive bird. , and these differences represent morphological experiments in early flight behavior in diverse birds.
Experts have said in their report that the new study shows that The first metatarsal was subject to selection during the dinosaur-bird transition to support a shorter bone. Once it reached its optimal size, less than a quarter of the length of the second metatarsal, it lost its evolutionary variation.
“However, there was greater evolutionary responsiveness between Mesozoic birds and their dinosaur relatives, which may have resulted in conflicting claims involving direct employment of locomotion and feeding of the hallux,” said co-author Dr. Thomas Stidham. For Cretonavis, such an elongated hallux probably derives from selection for raptorial behaviour.
abnormal morphology of The preserved scapulae and metatarsals in Cratonavis highlight the breadth of skeletal plasticity in early birds, said Dr. Zhonghe Zhou, co-author. Changes in these elements along the theropod tree show evolutionary branch-specific changes resulting from the interplay between evolution, natural selection, and ecological opportunity.