Feathers are a primitive trait among pennaraptoran dinosaurs, which today are represented by living birds, the only clade of dinosaurs to survive the end-Cretaceous mass extinction. Feathers are central to many important functions and therefore, maintaining plumage function is of great importance for survival. Thus, molt — by which new feathers are formed to replace old ones — is an essential process. The limited knowledge regarding molt in early pennaraptoran evolution is based largely on a single specimen of Microraptor, a small feathered dinosaur that lived 120 million years ago. In a new analysis of 92 feathered non-avian dinosaur and ancient bird fossils, paleontologists did not find additional molting evidence. They suggest that the evolution of the flight feather molt evolved with the development of powered flight, among ancient birds or a more derived subset of pennaraptoran dinosaurs, and as a response to the high dependence of this group on the flight feathers and the aerodynamic ability they impart.
“Molt is something that I don’t think a lot of people think about, but it is fundamentally such an important process to birds, because feathers are involved in so many different functions,” said Dr. Jingmai O’Connor, a researcher at the Field Museum of Natural History.
“We want to know, how did this process evolve? How did it differ across groups of birds? And how has that shaped bird evolution, shaped the survivability of all these different clades?”
In their study, Dr. O’Connor and Field Museum of Natural History postdoctoral researcher Yosef Kiat examined molting patterns in modern birds to better understand how the process first evolved.
In modern adult birds, molting usually happens once a year in a sequential process, in which they replace just a few of their feathers at a time over the course of a few weeks. That way, they’re still able to fly throughout the molting process.
Simultaneous molts in adult birds, in which all the…
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