An article published in the journal “Nature Communications” describes the study of a feathered dinosaur called Jianianhualong Tengi that lived about 125 million years ago in today’s China, in Liaoning Province. A team of researchers studied this animal that was part of the family of troodontids, dinosaurs with various bird-like features, and is very interesting for its asymmetrical feathers, a feature associated with flight.
China has long been the main nation for feathered dinosaurs’ discoveries but many fossils were been discovered on other continents, beginning with most of the specimens of the famous Archaeopteryx, the first feathered dinosaur uncovered. The various species discovered between the 19th and the first part of the 20th century led to the creation of the troodontid (Troodontidae) family and slowly paleontologists are reconstructing the evolution from dinosaurs to birds.
One of the characteristics studied in the reconstruction of the birds’ family tree is the presence of feathers. However, more and more fossils of dinosaurs show that plumage hadn’t evolved specifically among troodontids but was also spread in other groups and perhaps it was a common feature, it’s just that their fossil traces are limited. Luckily, in the Chinese site known as the Jehol Group fossils are generally very well preserved and Jianianhualong Tengi showed a really interesting plumage.
Jianianhualong Tengi had asymmetrical feathers, with long, stiff quills and barbs that are longer on one side than the other. Paleontologist Xing Xu, one of the authors of this study, pointed out that feathers asymmetry is a feature recognized as important for determining the origin of birds’ flight. This troodontid was similar in size to some modern birds being less than a meter (a little more than 3′) long but probably unable to fly. Despite that it had typical bird characteristics.
Probably Jianianhualong Tengi’s plumage provided some kind of aerodynamic support that allowed it to make long jumps to both escape predators and attack its prey. Paleontologists think that birds’ ability to fly evolved from that of dinosaurs that were able to someway glide just like this troodontid.
This doesn’t mean that Jianianhualong Tengi was a transitional species between dinosaurs and birds but it could be closely related to them. Paleontologists tend to think that troodontids are not birds ancestors but their cousins but the exact relationships among the various families is still subject to discussion. The fact that a troodontid had asymmetrical feathers could mean that this characteristic was inherited from a common ancestor of troodontids and birds that lived perhaps 160 million years ago.
Despite the many discoveries of feathered dinosaurs and primitive birds, there are still many hypotheses about their evolution. Often skeletons are incomplete and their plumage is in even worse conditions. In Jianianhualong Tengi’s case, feather asymmetry was detected in the tail of the original specimen described because it was visible but according to the researchers it was probably also present in its limbs’ feathers.
The study of the evolution of birds continues by restudying known species of troodontids and primitive birds comparing their various characteristics and examining each new specimen found in the meantime. Discoveries such as Jianianhualong Tengi’s asymmetric feathers can be a significant step forward.