Five million years ago, a massive sea monster may have eviscerated sharks and whales using gigantic teeth like this.

Murray Orr, an amateur fossil hunter, stumbled on this not-so-pearly-white in February while exploring Beaumaris Bay, a popular site for digging up ancient remains near Melbourne. At first, he had no idea what he was yanking out from the rocks.

“For a moment it looked like an artillery shell, and I thought I might blow my arm off,” he said in an email. “But then I saw the curving pointed end and knew it was a sperm whale tooth.”