Wing structure of modern birds evolved from dinosaurs

Are you an aspiring ornithologist? Yes, we are asking whether or not you are fascinated with birds and see yourself studying them someday. If yes, you would be delighted to know that the specialised wing structure of modern birds called ‘propatagium’ that helps them to make flights has evolved out of non-avian dinosaurs. How fascinating is that! 

So far, the evolutionary origin of this structure had remained a mystery. However, latest study of dinosaur fossils, especially their arm joints helped reveal how the modern wing structure of birds originated in the prehistoric creatures.   

The study conducted by a team of researchers based at the University of Tokyo’s Department of Earth and Planetary Science focussed on certain lineages of dinosaurs to find out more about the wing structure, feathers and bone structure of today’s birds. Why? Because previous research had shown how modern birds evolved from them. However, it was the wing structure that piqued the interest of the scientists.   

Called ‘propatagium’, it refers to the muscle (made of soft tissues) at the edge of the wing that connects the shoulder and wrist of the modern-day birds. This allows them to flap their wings and fly around easily. In fact, this feature is missing in other vertebrates and may have lost its function in flightless birds such as emu and ostrich.  

Anyhow, as revealed recently, this unique feature that allows the birds to make flight may have evolved from theropaud dinosaurs, more specifically Tyrannosaurus Rex and Velociraptor. So, in other words, what was arms in their case ended up being wings in case of present-day birds. But how this transition happened still remains unexplained. What’s interesting here is that, propatagium doesn’t fossilise well, meaning, not much evidence is left. As a result, the researchers had to come up with an innovative solution. What they did was to collect data about the angles of joints along the arms of these dinosaurs. Now, in modern birds, the wings cannot extend fully due to the presence of the propatagium, constraining the range of angles especially between the connecting sections. The scientists thought that if similar thing was visible in the dinosaur fossils, it would guarantee the presence of propatagium. Hence, it would mean, the wing structure of today’s birds evolved from them.   

Not only that, experimenting about wing structure also led to the chance discovery of a brand-new type of dinosaurs called maniraptoran theropods who had arm joints having soft tissues much like the propatagium. And guess what? All these evidences are from a period long before even the avian dinosaurs existed, i.e., the flight feature evolved.  

Can you guess what this means? That nobody can say for sure when propatagium came into existence and how it shifted from non-avian dinosaurs to modern-day birds. Let us hope the team finds out the answers soon! For now, they are guessing propatagium evolved not for the purpose of flying but for grasping objects. Strange, isn’t it?