A set of 75 million year-old fossils found in the badlands of southern Alberta is adding credence to the suggestion that dinosaurs used feathers to attract a mate, and not to take flight. The fossils, which are from the oldest feathered dinosaurs ever found, are also offering further proof that all ornithomimids — an ostrich like creature — were covered in feathers.
The image to your right is an artistic reconstruction of feathered ornithomimid dinosaurs by Julius Csotonyi.
According to researcher Darla Zelenitsky from the University of Calgary, the Upper Cretaceous Ornithomimus underwent a unique pattern of change in its feathery plumage over the course of its life. Prior to becoming an adult, the dinosaur would have been covered in down-like feathers. But as it got older, it developed larger feathers on the forearms which formed wing-like structures. This pattern, says Zelenitsky, is different from what we see in birds who develop feathered wings when they're still quite young.
The discovery also indicates that these dinosaurs did not use these filamentous feathers for any kind of flight or gliding. Because the wing-like forelimbs developed only in more mature individuals, paleontologists theorize that they were used later in life for such things as attracting a mate or egg brooding. Moreover, because ornithomimids were over 150 kilograms (330 lbs), there would have been simply too big to fly.
And interestingly, these specimens, which were found back in 2008 and 2009, have pushed back the date of the earliest wings by about 10 million years. But because they weren't used for flight, paleontologists think they must have evolved for completely different reasons — and only later did they endow smaller, lighter versions of dinosaurs with flight.
Check out the entire study at Science.
Inset image Leah Hennel , Calgary Herald.