May 8, 2002 Imagine a one-ton Big Bird à la Sesame Street, but instead of friendly “hands,” he has Freddie Claws. That’s basically what the Therizinosaurid dinosaur looks like that geologist David Gillette’s team from the Museum of Northern Arizona (MNA) found in Kane County, Utah.
“This is a one ton plant-eating carnivore with really bizarre claws,” said Gillette. “It had slender arms and really long bones in the hand with bladed claws that look like sickles. With the sheath, the claws are about 15 inches long.”
In 2001, Gillette’s crew found an almost complete skeleton, which is a rare find. Some Therizinosaurid remains found in China caused quite a stir because they were found with feather-like structures on them. The idea that these creatures were among the ancestors of birds has been gaining increased acceptance.
Gillette will present a preliminary report on their discovery May 7 at the Geological Society of America Rocky Mountain Section Meeting at the Southern Utah University campus.
He will also report on another uncommon find—skin impressions of a duck-billed dinosaur known as a Hadrosaur. Gillette’s group found the impressions while excavating the dinosaur’s tail in the new Grand Staircase-Escalante National Monument (GSENM) in Kane County.
“This is the second reported discovery of skin impressions in Utah,” Gillette said. “On the global scale, however, this is a rare occurrence. This was a great discovery, especially in the context of the Hadrosaur with an articulated tail--that means the bones were still connected--that extended from the base of the tail (at the hips) to near the tip, about 13 feet long. In addition, the tendons that in life held the tail rigid were still preserved in life position.”
The Grand Staircase-Escalante National Monument is about two million acres large and much of it is exposed and eroded rock, so fossils are usually only found in unrecognizable bits and pieces. But the MNA discovery was different.
“The rear half of the body was in beautiful state of preservation and in articulation. The discovery of the skin impressions came during the excavation, to our great delight and surprise,” Gillette said. “I would describe the skin as pebbled, with radiating grooves in each bump. The bumps were polygonal, nearly equilateral diamonds, pentagons, and hexagons. This texture surely added strength and toughness to the skin, which in turn would resist decay following death and burial. The carcass did not decay much prior to burial, but had to be desiccated to resist decomposition by bacteria--that is, the local environment must have been very dry.”
Scott Sampson from the Utah Museum of Natural History will provide updates on his and his team’s discoveries from GSENM at the same May 7 session as Gillette—“Paleontological Research in Grand-Staircase Escalante National Monument and Surrounding Area.”
Their findings include two previously unknown horned dinosaurs (ceratopsians), a partial skull of a dome-headed dinosaur (pachycephalosaur), a partial skeleton of a large-bodied tyrannosaur that is the first tyrannosaur from this time period in Utah, and the remains of two previously unknown giant crocodiles. Research for this project was funded by GSENM as part of a collaborative paleontological survey.
“Given how little is known of the dinosaurs from GSENM, chances are high that most of the dinosaur remains represent species new to science,” Sampson said. “Now the goal is to find enough of each of these ancient beasts to establish that they do represent new species. Our efforts and those of others over the past several years suggest that GSENM has perhaps greater potential to yield new and interesting kinds of dinosaurs than any other region in North America.”
Based on different types of Late Cretaceous plants and animal discoveries in Montana and Alberta versus those found in New Mexico and Texas, Sampson and others speculate that Utah may be an important boundary area between two major "biozones."
“To really understand this paleoecological story, however, will require a good record from the Late Cretaceous of Utah,” Sampson said. “And GSENM will provide that record.”
Brent H. Breithaupt, from the University of Wyoming’s Geological Museum, will take a look at what he calls “Theropod family values” via a “live-action” glimpse of their lives through intensive study of over 1,000 dinosaur tracks at the Red Gulch Dinosaur Tracksite in northern Wyoming. He will present his report May 8 at the Stratigraphy, Paleontology, Paleobotany, Archaeological Geology, and History of Geology session at the meeting.
“We have evidence of gregarious carnivorous dinosaurs. These are groups of animals moving together,” Breithaupt said. “Trace fossils such as tracks are unique in that they actually preserve the activities of ancient animals. In addition, as we have a very large and statistically valid database we can make some unique interpretations. This is important as evidence for gregarious carnivorous dinosaurs is relatively rare.”
Using data from a variety of resources including aerial photography of the entire tracksite and close-range photogrammetric images of a single track, Breithaupt and his co-authors speculate there were family groups, ranging from yearlings to adults, interacting near their nesting area by a shore.
“The data also suggest a certain level of parental care and the level of dependence of the young dinosaurs, as we have juveniles traveling with adults” he said. “From what we know about dinosaur growth, it appears that they grew at the same rates as some modern ground birds such as ostriches and emus. If our dinosaurs represent animals of different ages of the same species then the smallest ones can't be very old--a year or perhaps less. Little animals of this sort probably aren't going to travel long distances during the first year. Thus, they were probably relatively near a large ground nesting area. If we accept the paradigm of theropod dinosaurs being similar to modern birds, then some of the behaviors and family structures may be similar as well.”
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