A Feathered Terror From Utah

This week, another “new” dinosaur was officially announced to the world. Like several other discoveries over the past few years, this one was unearthed from rocks of the Late Cretaceous Kaiparowits Formation in Grand Staircase-Escalante National Monument (GSENM), southern Utah. Over the past decade, the Kaiparowits Basin Project, which I have the pleasure of heading up, has yielded about a dozen new dinosaur varieties from these sediments, amongst them duck-billed hadrosaurs like Gryposaurus and horned ceratopsians like Kosmoceratops. Thanks to the work of geologists and paleobotanists, we know that these animals lived about 76 million years ago in a wet, often swampy setting about 100 km from the coast of an inland sea.

Over the past decade, tantalizing bits and pieces of a small, carnivorous “troodont” theropod have been found in the Kaiparowits Formation. Closely akin to Velociraptor, troodonts are a clan of feathered “raptors” with sickle claws tipping the second toe of each foot. They were lightly built runners with some of the largest brains for their body size of any dinosaur. Most of our GSENM troodont fossils have consisted of random teeth, augmented by a few isolated skull and limb bones. But a couple of years ago, graduate student Michael Knell from Museum of the Rockies in Bozeman, Montana—while working in GSENM with Monument Paleontologist Alan Titus—found a partial skeleton that turned out to belong to this mystery theropod.

A team of workers consisting of Lindsay Zanno (University of Wisconsin-Parkside), David Varricchio (Montana State University), Patrick O’Connor (Ohio University), Alan Titus, and Michael Knell has just published their conclusions about this ancient little beast in the online journal PLoS ONE [1].

Talos, as it was dubbed, is the first troodont to be named from North America in more than 75 years. (In Greek mythology, Talos was a winged bronze figure who protected the island of Crete by throwing large stones at invading ships.) The vast bulk of fossils attributed to this group have been found in Asia, including the famous sleeping dinosaur (Mei long), as well as many eggs and nests. With few exceptions, the remains of North American troodonts have tended to be much scrappier. In life, Talos would have been about 6 feet long, but most of that length consisted of neck and tail, so the animal would have weighed in at a paltry 80 lbs or so. Mike Knell’s key specimen consists of most of the back limb plus a few other odds and ends. Most striking of all is the virtually complete foot with the lethal-looking claws.

One of those claws shows distinct signs of injury, a visual diagnosis that was confirmed with CT scanning of the bones. Particularly since the remainder of the foot was uninjured, this finding suggests that, at least occasionally, troodonts put their sickle claws “in harm’s way,” as Zanno colorfully puts it. Although it has long been assumed that these claws were used as predatory weapons, Talos offers the first fossilized evidence of such behavior. Whatever the cause of the injury, this particular animal survived for some time after the initial trauma and infection.

Many readers of this blog will know that Late Cretaceous North America was subdivided into a pair of landmasses—Laramidia in the west and Appalachia in the east—by high sea levels that flooded the central region of the continent. For about 25 million years, Laramidian dinosaurs evolved in isolation from the rest of the world. Most remarkable is the fact that this diminutive landmass, less than one fifth the size of present day N. America, hosted at least two distinct dinosaur faunas: one in the north and another in the south. Talos provides yet another unique addition to the southern fauna, deepening the mystery of how so many dinosaur varieties managed to co-exist on such a small chunk of real estate.

Finally, I have to thank the Talos authors, who have graciously called the second half of Talos’ name “sampsoni.” I am honored to have this little predator named after me, and had to chuckle when I heard the news. Until recently, the name Troodon was known only to professional paleontologists and a few die-hard kid enthusiasts. However, millions of fans of the PBS KIDS series Dinosaur Train (for which I serve as the science advisor and host) are now well aware of Troodon, because these animals run the famous train, and frequently tell anyone who will listen, “We are the smartest dinosaurs, ya know!”

The bones of Talos will be on exhibit for the first time in the brand new Museum of Natural History of Utah in Salt Lake City (previously the Utah Museum of Natural History), which is set to open to the world on November 17^th!

References

1. Zanno LE, Varricchio DJ, O’Connor PM, Titus AL, Knell MJ (2011) A New Troodontid Theropod, Talos sampsoni gen. et sp. nov., from the Upper Cretaceous Western Interior Basin of North America. PLoS ONE 6(9): e24487. doi:10.1371/journal.pone.0024487