September 20, 2011
New Raptor Species Announced
A graduate student from Montana State University is part of a team of researchers that revealed a new species of raptorial dinosaur to the public on Monday, the first definitive troodontid theropod discovered from the Late Cretaceous Period of North America in more than 75 years.
MSU doctoral student Mike Knell, MSU paleontologist David Varricchio, three colleagues, and lead researcher Lindsay Zanno, from the University of Wisconsin-Parkside and the Field Museum of Natural History in Chicago, published their findings in the journal PLoS One.
Knell is credited with the discovery of the fossil in one of the last unspoiled dinosaur fossil beds in the United States. It was found in the 1.9-million-acre Grand Staircase Escalante National Monument in southern Utah. At least fifteen other new dinosaur species have been found here in the past decade.
He found the fossil in 2008 while combing the badlands for turtle fossils as part of his dissertation research. He stumbled onto the dinosaur fossil at the same spot where he found a 75-million-year-old turtle fossil that was only the second ever to contain eggs. He published findings on the turtle fossil in 2009.
“I was surprised when I learned that I had found a new dinosaur,” said Knell. “It is a rare discovery, and I feel very lucky to be part of the exciting research happening here in the monument.”
Dubbed Talos sampsoni, the new dinosaur specimen is a member of a rare group of feathered, bird-like theropod dinosaurs whose North American evolution has been the source of long-time debates, particularly for lack of decent fossil material.
The genus name “Talos” is in homage to a winged bronze giant in Greek mythology that could run at lightning speed and was succumbed to a wound to his ankle. The species name “sampsoni” is in honor of Scott Sampson of the PBS series “Dinosaur Train,” and a curator at the Utah Museum of Natural History.
“Finding a decent specimen of this type of dinosaur in North America is like a lighting strike,” Zanno said, referring to the fact that troodontids are known nearly exclusively from Asia. “It's a random event of thrilling proportions.”
The researchers noted that the dinosaur sheds new light on several questions, including the function of a greatly enlarged talon and how the dinosaurs evolved on the “lost continent” of Laramidia (western North America) during the Late Cretaceous Period. The researchers also expressed their interest in the fact that Talos appeared to have had an injury.
Like other raptor dinosaurs, Talos possessed unusually large, sickle-like claws on the second toes of each foot, which it held off the ground like folded switchblades. These talons were thought to be used as weapons, thanks to a discovery 30 years ago in Mongolia of a Velociraptor locked in combat with its prey. Now, the injured claw of the new dinosaur sheds even more light on how they lived with and used these deadly weapons.
Discovering that the second toe on Talos´ left foot was oddly straight and malformed was exciting, said Zanno. “When we realized we had evidence of an injury, the excitement was palpable. An injured specimen has a story to tell,” she added.
Zanno explained that injuries relate to function; the manner in which an animal was hurt indicates something about what it was doing in life.
Zanno and her team ran individual bones through a CT scanner and found that the Talos injury was restricted to its toe. The discovery suggests that the toe was either bitten or fractured and then suffered from a serious, localized infection.
“People have speculated that the talon on the foot of raptor dinosaurs was used to capture prey, fight with other members of the same species or defend the animal against attack,” Zanno said. “Our analysis supports the idea that these animals regularly put this toe in harm's way.”
“Talos was fleet-footed and lightly built. This little guy was a scrapper,” she said.
“Normally we think that the most pristine fossils we can find perhaps yield the most important information, but in fact sometimes it's the beat-up, damaged, injured specimens that can give you clues about the biology of an extinct animal you wouldn't have otherwise,” Zanno told LiveScience.
The researchers were intrigued that the injured toe showed signs of the kind of changes in bone that occur over many weeks or months, suggesting that Talos lived with the injury for a long time.
“Although we could see damage on the exterior of the bone, our microCT approach was essential for characterizing the extent of the injury, and importantly, for allowing us to better constrain how long it had been between the time of injury and the time that this particular animal died,” said researcher Patrick O'Connor from Ohio University.
“It is clear from the bone remodeling that this animal lived for quite some time after the initial injury and subsequent infection, and that whatever it typically did with the enlarged talon on the left foot, whether that be acquire prey or interact with other members of the species, it must have been capable of doing so fairly well with the one on the right foot,” O´Connor noted.
Other raptor footprints discovered show that the switchblade talon is held off the ground and not used for walking. “Our data support the idea that the talon of raptor dinosaurs was not used for purposes as mundane as walking,” Zanno noted. “It was an instrument meant for inflicting damage.”
It is unclear what Talos may have eaten. “Many are still debating over what its relatives ate,” said Zanno. “My recent research suggests it was probably either a carnivore or an omnivore, eating some degree of prey.”
Talos live in a warm tropical world with no polar ice caps. In what is now North America, a shallow seaway ran from the Gulf of Mexico through to the Arctic Ocean, dividing the continent into two landmasses -- Appalachia and Laramidia -- for several million years.
“The area was basically the complete antithesis of what it is now,” said Zanno. “It was extremely wet then, a very, very lush environment, almost swampy, and regularly bombarded by massive storms coming in off the seaway that divided North America at the time.”
Mysteriously, the dinosaurs of Laramidia appeared to be unusually diverse. Normally, large animals are expected to span the whole area in which they live, as is the case with many modern predatory animals, and this might be expected to prove true on relatively smaller continent such as Laramidia. However, dinosaurs from the Utah formation where Talos was found are entirely distinct from ones living just a few hundred miles north in Montana and Alberta.
“We already knew that some of the dinosaurs inhabiting southern Utah during the Late Cretaceous were unique, but Talos tells us that the singularity of this ecosystem was not just restricted to one or two species -- rather, the whole area was like a lost world in and of itself,” said Zanno.
Now, we are trying to answer how this diversity might have developed, she said. “Some preliminary research done by a colleague of mine suggests there may have been geographic barriers -- mountain ranges and rivers -- dividing up populations, keeping them isolated for long enough to become new species.”
“We're going to continue scouring these badlands -- this area is one of the last dinosaur graveyards anywhere in the United States,” said Zanno.
Funding for the research was provided in part by the National Science Foundation, the Field Museum of Natural History, the Ohio University Heritage College of Osteopathic Medicine, and the Bureau of Land Management.
Zanno's research was supported by a John Caldwell-Meeker Fellowship and by a Bucksbaum Fellowship for young scientists.
The bones of Talos will be on exhibit for the first time in the Past Worlds Observatory at the new Utah Museum of Natural History in Salt Lake City.
Image 1: This image shows the fleshed-out reconstruction of Talos sampsoni, a new troodontid dinosaur found in the Upper Cretaceous Kaiparowitz Formation, Grand Staircase-Escalante National Monument in southern Utah. (Artwork by Jorge Gonzales).
Image 2: The leg bones of Talos sampsoni peek out from mudstones of the Late Cretaceous Period in southern Utah. This is the first time the skeleton has been exposed to daylight in 76 million years. (Photo courtesy of Alan Titus).
On the Net:
- Montana State University
- PLoS ONE
- University of Wisconsin-Parkside
- Field Museum of Natural History
- Utah Museum of Natural History
- Ohio University