By
Carrah Bechtel
Arizona Daily Wildcat
Fossils of Early Cretaceous 'megafauna' found after student stops to change a flat tire
A remote site 25 miles outside of Tucson yielded a rich discovery of dinosaur bones for one UA student.
"I just had a feeling I was going to find something out there," said Gregory Cranwell, a geological engineering junior.
Cranwell and his wife got a flat tire a few months ago as they were driving near Sonoita, Ariz. Cranwell managed to patch it up, but before he drove away he took a long look at the surrounding hills.
"I had an instinctual feeling that I had to keep looking at those hills," he said.
He noticed the color and shape of the rock, which enabled him to characterize it as sedimentary. Cranwell knows that sedimentary rock deposits are prime places to search for dinosaur bones.
"Something told me they were sedimentary," he said. "I got out of my car and examined more closely - sure enough, they were. I told my wife that I was going to find dinosaur bones (there)."
He checked out a map of the area to make sure the land was legal for him to walk on.
He contacted Robert McCord, curator of paleontology for the Mesa Southwest Museum, and obtained a permit for the land. A person with a Ph.D. must be present at the site as an investigator and since Cranwell is a research assistant for the museum, McCord proved to be the perfect contact.
On the first day of digging, Cranwell's gut feeling proved correct when he discovered dinosaur bones.
"It was really exciting," he said. "I began mapping everything out and getting in contact with people who could help me."
Cranwell discovered the earliest known sauropod in Arizona. A sauropod is a relative of the Brachiosaurus, a four-legged plant eater. Cranwell's sauropod lived during the Early Cretaceous period, part of the Mesozoic Era, about 97-144.5 million years ago.
The piece found was a right fibula - a bone in the lower leg - and a chest plate, which is very similar to the human sternum.
His other discovery included bones from a nodosaurid. This heavily built, armored plant eater was about the size of a car, and looked like a giant horned toad with large spikes, Cranwell said.
Pieces of the nodosaurid's osteoderm - or bony skin which functioned as body armor - were also found. These resemble the same types of armor found on a crocodile.
The two dinosaur specimens represent megafauna - or large animals found in their environment - Cranwell said.
Other fossils found in the area included those of turtles, crocodiles, a freshwater mussel bed and an entire wall of plant fossils.
"There is the potential to find a lot more bones and fossils in this area," Cranwell said. "This is a missing piece in dinosaur history for Arizona. These are the only early Cretaceous animals found in Arizona so far.
"This is very significant for us as humans to help us figure out where we came from."
