PLANO -- Between the baseball field and the tennis courts at Plano West High School you'll see what looks like a dried up creek bed.

"Having a formation in our backyard is going to be very, very rare, and being able to find anything, especially in 'austin chalk' is very rare," said AP Biology Teacher Wesley Kirpach.

Turns out that just feet from the class room -- students have access to prehistoric geologic formation. For the last decade Kirpach's students have used this strip of land as an archeological dig site.

A few weeks back, Junior Lillia Blasius stumbled on something special.

"I saw the outline of a tooth in the ground and I was like -- 'that's really interesting, it must be something."

According to Kirpach the tooth she found believed to be from an 18-foot long shark that lived some 85 million years ago -- specifically a Cretoxyrhina Mantelli.

"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," Blasius said.

This piece of history has already been cataloged and will be available for researchers at SMU to examine.

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