When several Plano West High School students dug in a nearby creek bed with their biology class, they made a rare paleontological find.

Junior Lillia Blasius and senior Ashley Chanpong chose to search where none of the other students went, and it paid off, the school's student paper, BluePrints, reports.

Lillia discovered a tooth believed to be from an 18-foot shark that lived about 85 million years ago, WFAA-TV (Channel 8) reported.

"It was peeking out of the surface and she saw the tooth shape and picked it up," Ashley said.

Previous classes have searched the area, but AP biology teacher Wesley Kirpach told WFAA it's "very, very rare" to find anything, especially in Austin chalk.

"They were talking about how some kids over the years have found shark teeth and things like that, and I didn't think I was actually going to find anything — so it was really surprising when I found it," Lillia said.

The piece has been cataloged and will be available for researchers at Southern Methodist University.

"Every little piece that they uncover, every rock they turn over is a rock that someone has never seen before in human history," Kirpach said.