A new fossil specimen, named Norellraptor barsboldi, has been analyzed by an international group of scientists from China and Italy and was described on Tuesday in an article published in Nature Communications. This discovery changes the understanding of how dinosaurs acquired the ability to fly.
This exceptionally well-preserved specimen of a microraptorine (small dinosaurs with feathers and wings) was found in the Jiufutang geological section (China). This area belongs to the Lower Cretaceous period and dates back to 145 to 100 million years ago.
Microraptorines were small predatory dinosaurs that resembled birds and were close relatives of them. Previously found fossils (most of which were discovered in China) showed that some microraptorines had long feathers on both forelimbs and hindlimbs, suggesting adaptation to flight.
For a long time, paleontologists debated whether the ability to fly or glide arose only once in the common ancestor of Paraves (a group that includes microraptorines and birds), or if the necessary traits evolved independently in several instances.
The study presented a 57-centimeter fossil that preserved parts of plumage and, according to analysis, was at least three years old at the time of death. By comparing the flight characteristics of the new specimen with other microraptorines and primitive bird lineages (Avialae), it was found that these small predators and primitive birds share 57 morphological features related to flight, accounting for about 30% of the essential physical traits required for flight.
Nevertheless, despite the presence of many shared structures, researchers believe that birds and dinosaurs did not inherit a single 'blueprint.' Instead, they developed their flying apparatuses in a completely 'independent and convergent' manner, responding to similar needs and different evolutionary pressures.
According to the authors, the main evidence for this divergence is the order in which their bodies evolved. In the bird lineage, evolution first transformed the shoulder girdle and wing joints before changing the hand. In the case of microraptorines like Norellraptor, the initial changes involved shortening finger bones to reduce grasping function. The elongation of the sternum and changes in the shoulders appeared only much later.
The authors argue that this divergence in the temporal sequence of changes proves the absence of a latent or common genetic model guiding both species. Furthermore, microscopic analysis of the bones of Norellraptor's arm showed that its limbs grew with an intermittent and highly specific rhythm. This osteohistological pattern differs from the developmental mechanisms observed in modern flying birds, confirming that the wings of microraptorines formed under their own biological dynamics.
The Norellraptor study refutes the paradigm of single origin of flight, demonstrating that the ability to fly was not a unique innovation in dinosaur history, but rather an 'evolutionary experience' that nature successfully replicated through entirely different paths.