A college student on a field trip with his introductory paleontology class has discovered a 5-foot-long skull from what is believed to be an 80-million-year-old horned dinosaur called a chasmosaurus.
It is the only complete dinosaur skull ever found in Big Bend National Park in Texas and provides the best evidence that the chasmosaurus roamed what is now the southern United States. Most chasmosaurus fossils have been found in Wyoming and Canada.
The student, Thomas Evans, a 21-year-old biology major at the University of Chicago, said he first noticed what turned out to be a piece of a horn poking up about 6 inches from the sediment.
"I was just walking, and I saw something to the right that looked like a fossilized bone," Mr. Evans said. As he and a graduate student brushed away some of the sediment, they thought it was a pelvic bone. Further excavation revealed the nearly complete skull.
"I just can't believe I noticed anything," Mr. Evans said.
The field trip was led by Dr. Paul Sereno, a University of Chicago paleontologist who uncovered the world's oldest known dinosaur Argentina in 1988.
"Fossils this rare and this complete have never been found in this park," Mr. Sereno said. "It's a once-in-a-century find in this region."
Tom Lehman, a professor of geology at Texas Tech University in Lubbock, said, "Scientists have been searching the park for 50 years, finding thousands of isolated bones, but never anything like this."
Now with the skull, they will be able to put together the pieces to form a nearly complete skeleton.
The chasmosaurus is related to the better-known triceratops. Both dinosaurs were plant eaters with huge heads and bulky bodies.
The skull has a pair of 2-foot-long brow horns and a shorter, curved nose horn. Behind the head is a bony frill that looks something like a shield. Mr. Sereno estimates that the dinosaur weighed about 5 tons and was about 25 feet long.
"This is a very important discovery for understanding the evolutionary tree of horned dinosaurs," Mr. Sereno said. "It is quite likely that this dinosaur was distinct from its northern relatives."
While Mr. Evans is not planning graduate work in paleontology in the immediate future, he said, "My interest in the field is definitely heightened."