MSU doctoral student Mike Knell found the fossil in southern Utah in one of the last pristine dinosaur graveyards in the United States.
The dinosaur -- dubbed Talos sampsoni - is the first definitive troodontid theropod to be named from the Late Cretaceous Period of North America in more than 75 years, according to Knell, MSU paleontologist David Varricchio and three colleagues who published their findings in the journal PLoS One. Lead author and head of the study team is Lindsay Zanno from the University of Wisconsin-Parkside and the Field Museum of Natural History in Chicago.
The researchers said the newly found dinosaur is a member of a rare group of feathered, bird-like theropod dinosaurs whose evolution in North America has been a longstanding topic of scientific debate. The scientists said the dinosaur sheds new light on several questions, including the function of a greatly enlarged talon and how dinosaurs evolved on the "lost continent" of Laramidia (western North America) during the Late Cretaceous Period when dinosaur diversity flourished. The fact that Talos appears to have been injured added another level of interest.
Knell discovered the fossil in 2008 while scouring the badlands of the Kaiparowits Formation for fossil turtles as part of his dissertation research. He stumbled across the remains while working in the Grand Staircase-Escalante National Monument. It was there that he also found a 75-million-year-old turtle fossil that was only the second in the world containing eggs. Knell took the turtle fossil to Bozeman Deaconess Hospital for a CT scan in 2009 and has since presented his findings about that fossil.
"I was surprised when I learned that I had found a new dinosaur," Knell said. "It is a rare discovery, and I feel very lucky to be part of the exciting research happening here in the monument."
Zanno said, "Finding a decent specimen of this type of dinosaur in North America is like a lightning strike. It's a random event of thrilling proportions."
Discovering that the second toe on the dinosaur's left foot was oddly straight and malformed was also exciting, because it indicated an injury, Zanno said.
"When we realized we had evidence of an injury, the excitement was palpable," she commented. "An injured specimen has a story to tell."
The researchers explained that injuries relate to function; the manner in which an animal was hurt indicates something about what it was doing in life. They added that the injured raptor foot provides new evidence about how the dinosaur used that toe and claw.
Zanno and her team ran individual bones through a CT scanner and discovered that the Talos injury was restricted to its toe. The discovery suggested that the toe was either bitten or fractured and then suffered from a serious, localized infection, Zanno said.
"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."
Troodontid theropods are closely related to birds. The Talos sampsoni was estimated to weigh about 84 pounds - neither the smallest nor largest troodontid known.
"Talos was fleet-footed and lightly built," Zanno said. "This little guy was a scrapper."
The research team added that Talos sampsoni is the newest member of a growing list of new dinosaur species that have been discovered in Grand Staircase Escalante National Monument. The monument is the largest and most recently designated national monuments.
"The area has turned out to be a treasure trove of new dinosaur species with at least 15 collected in just the past decade," Zanno said.
"We already knew that some of the dinosaurs inhabiting southern Utah during the Late Cretaceous were unique," she said. "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."
Zanno is an assistant professor of anatomy at the University of Wisconsin-Parkside and a research associate at the Field Museum of Natural History in Chicago. Other members of the research team besides Varricchio and Knell were Bureau of Land Management paleontologist Alan Titus, leader of a decade-long paleontology reconnaissance effort in the monument; and Patrick O'Connor, associate professor of anatomy at the Ohio University Heritage College of Osteopathic Medicine.
The bones of Talos sampsoni will be exhibited for the first time in the Past Worlds Observatory at the new Utah Museum of Natural History in Salt Lake City.
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.
Evelyn Boswell, (406) 994-5135 or firstname.lastname@example.org