April 17, 2009
By MATTHEW HAAG
The Dallas Morning News
Liz Arroyos and her classmates scoured the blue-gray creek bottom behind her school.
The Plano West Senior High School students were outside to learn a little something about digging for clues to the past. When class ended, she hoped she had something good in the rocks she clasped in her hands.
"I'm not really a paleontologist," said Liz, a junior at the school. "I was just messing around and picked up something I thought the teacher would like."
Biology teacher Wesley Kirpach looked at the rocks. A brittle brown material piercing a piece of chalk caught his attention it was a bone, some type of reptile.
What was inside Liz's rock would not only please her teacher, but ultimately bring excited scientists from Southern Methodist University to the school grounds for a full-fledged dig that took place last week.
Kirpach's students have ventured down to the creek, which extends about 15 feet wide and 100 yards long, each school year when they study evolution and fossils. Students have routinely discovered shark teeth and tiny fish fossils.
But Liz's find was unique, Kirpach said. So he immediately wanted to see what else could be buried nearby. He hurried to the school's floral design class, borrowed a broom and rushed back to the creek.
"If you find a piece of bone broken, it's common that the rest of the body might be in the rock," Kirpach said.
He swept gravel off the creek bed to expose the top layers of rock. He bent down and looked harder. Nothing. He brushed his hand across the surface. Still nothing.
"Then the bell rang," Kirpach said.
He said he decided to give up and headed back to the school. But as he walked out of the creek bed, he stepped on a footlong object slightly bulging from a white rock. He looked down and saw what appeared to be five fossilized vertebrae bones linked together.
"Sheer luck," Kirpach said. "That's when I got excited."
Mike Polcyn, a paleontologist at SMU, soon arrived and identified the object. Kirpach had stepped on fossilized neck bones of a Platecarpus, a 12- to 15-foot marine lizard with flippers and multiple rows of peg-shaped teeth. It probably roamed a large sea that covered most of Texas 85 million years ago.
Polcyn then took the bone fragment Liz found and slid it behind the exposed bones. A perfect fit.
"It's pretty rare," he said. "There are only a couple specimens known in Texas."
Polcyn and a team of SMU graduate students returned to the creek bed last week and cut out a 250-pound rock surrounding the fossil. Student Ben Zhao and several of his Plano West classmates stood several yards down the creek and sifted rocks. They searched for more Platecarpus fossils that recent storms might have washed downstream.
Zhao, 19, discovered a minuscule bone chip that most likely belonged to the creature.
"Whenever we saw something that looked special, we had Mr. Kirpach check it," said Zhao, a junior at the school.
The massive rock now sits in a science lab at SMU, and Polcyn said he'll probably begin chipping away at it during the next few months. What lies beneath is unknown, he said. But there's a good chance the marine lizard's skull is hidden inside.
Kirpach said he hopes to take his students on a field trip to see part of the excavation.
"It's unreal," he said. "It's one of those things you are supposed to read about, not see it."
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