Fossils of first feathered dinosaurs from North America discovered: Clues on early wing uses

The ostrich-like dinosaurs in the original Jurassic Park movie were portrayed as a herd of scaly, fleet-footed animals being chased by a ferocious Tyrannosaurus rex. New research published in the journalScience reveals this depiction of these bird-mimic dinosaurs is not entirely accurate -- the ornithomimids, as they are scientifically known, should have had feathers and wings.

The new study, led by paleontologists Darla Zelenitsky from the University of Calgary and François Therrien from the Royal Tyrrell Museum of Palaeontology, describes the first ornithomimid specimens preserved with feathers, recovered from 75 million-year-old rocks in the badlands of Alberta, Canada.

This is an artistic reconstruction of feathered ornithomimid dinosaurs found in Alberta

"This is a really exciting discovery as it represents the first feathered dinosaur specimens found in the Western Hemisphere," says Zelenitsky, assistant professor at the University of Calgary and lead author of the study. "Furthermore, despite the many ornithomimid skeletons known, these specimens are also the first to reveal that ornithomimids were covered in feathers, like several other groups of theropod dinosaurs."

The researchers found evidence of feathers preserved with a juvenile and two adults skeletons ofOrnithomimus, a dinosaur that belongs to the group known as ornithomimids. This discovery suggests that all ornithomimid dinosaurs would have had feathers.

The specimens reveal an interesting pattern of change in feathery plumage during the life of Ornithomimus. "This dinosaur was covered in down-like feathers throughout life, but only older individuals developed larger feathers on the arms, forming wing-like structures," says Zelenitsky. "This pattern differs from that seen in birds, where the wings generally develop very young, soon after hatching."

This discovery of early wings in dinosaurs too big to fly indicates the initial use of these structures was not for flight.

"The fact that wing-like forelimbs developed in more mature individuals suggests they were used only later in life, perhaps associated with reproductive behaviors like display or egg brooding," says Therrien, curator at the Royal Tyrrell Museum and co-author of the study.

Until now feathered dinosaur skeletons had been recovered almost exclusively from fine-grained rocks in China and Germany. "It was previously thought that feathered dinosaurs could only fossilize in muddy sediment deposited in quiet waters, such as the bottom of lakes and lagoons," says Therrien. "But the discovery of these ornithomimids in sandstone shows that feathered dinosaurs can also be preserved in rocks deposited by ancient flowing rivers."

Because sandstone is the type of rock that most commonly preserves dinosaur skeletons, the Canadian discoveries reveal great new potential for the recovery of feathered dinosaurs worldwide.

The fossils will be on display this fall at the Royal Tyrrell Museum in Drumheller, Alberta.

All teeth and claws? New study sheds light on dinosaur claw function

Theropod dinosaurs, a group which includes such famous species asTyrannosaurus rex and Velociraptor, are often regarded as carnivorous and predatory animals, using their sharp teeth and claws to capture and dispatch prey. However, a detailed look at the claws on their forelimbs revealed that the form and shape of theropod claws are highly variable and might also have been used for other tasks

Inspired by this broad spectrum of claw morphologies, Dr Stephan Lautenschlager from Bristol's School of Earth Sciences studied the differences in claw shape and how these are related to different functions.

His research focussed on the therizinosaurs, an unusual group of theropods which lived between 145 and 66 million years ago. Therizinosaurs were very large animals, up to 7m tall, with claws more than 50cm long on their forelimbs, elongated necks and a coat of primitive, down-like feathers along their bodies. But in spite of their bizarre appearance, therizinosaurs were peaceful herbivores.

Dr Lautenschlager said: "Theropod dinosaurs were all bipedal, which means their forelimbs were no longer involved in walking as in other dinosaurs. This allowed them to develop a whole new suite of claw shapes adapted to different functions."

In order to fully understand how these different claws on the forelimbs were used, detailed computer models were created to simulate a variety of possible functions for different species and claw morphologies.

The dinosaur claws were also compared to the claws of mammals, still alive today, whose function (that is, how and for what the claws are used) is already known.

In the course of evolution, several theropod groups, including therizinosaurs, changed from being carnivores to become plant-eaters. This new study reveals that, during this transition, theropod dinosaurs developed a large variety of claw shapes adapted to specific functions, such as digging, grasping or piercing.

Dr Lautenschlager said: "It's fascinating to see that, with the shift from a carnivorous to a plant-based diet, we find a large variety of claw shapes adapted to different functions. This suggests that dietary adaptations were an important driver during the evolution of theropod dinosaurs and their transition to modern birds."