Construction workers made a strange discovery while working in Scotts Valley, CA earlier this month. According to a report from UPI, a team of archaeologists was brought in after construction stopped to begin excavating what they discovered was an ancient whale fossil.

The ancient whale fossil was unearthed in the beginning of September by developers working on a residential project in the Santa Cruz Mountains. Developers called on a team of archaeologists from Paleo Solutions, an LA County-based firm that specializes in the excavation of old and sensitive artifacts and fossils.

By September 17, archaeologists were ready to begin excavating the fossils by carefully digging around them using small shovels and hand tools. The ancient whale’s bones were extremely fragile, and they remained attached to the rock during the excavation.

Archaeologists dug around the entire body of the ancient whale and covered it in a plaster casing. They believe the whale fossil made its way into the middle of the California mountains by being moved around with the soil as tectonic plates shifted over millions of years. According to Scott Armstrong, a paleontologist from Paleo Solutions, “Most places where you see a hill, somewhere there’s a fault line nearby pushing it up. They’re relatively inactive faults. But year, it’s from lifting thousands, maybe millions of years ago.”

Researchers think the ancient whale fossil could be as old as 4 million years old. At this time, it’s unclear which species the whale belongs to.