Perhaps it was inevitable that as Los Angeles expanded its vestigial subway system into a public transit option worthy of a major city fossils would turn up. Los Angeles was built in a place pockmarked with tar pits, and one of the sites on the extension of the Purple Line is at Wilshire and La Brea, not far from the famous La Brea Tar Pits, which daily yields new finds.

Late in November, construction crews found another one, the Los Angeles Times reports. The first piece of an ancient animal that they discovered was a shattered tusk, three feet long, followed by a mastodon tooth. This week, a specialist who monitors the site for fossil finds located another set of tusks, along with a giant skull.

This second set of fossils looks to be the head of an ancient elephant. This elephant lived back in the Ice Age, the Times reports, but scientists aren’t yet sure exactly what type of ancient elephant it was.

Because this area is so rich with fossils, the Metro already has a plan for how to handle such finds—they’re already built into the project’s timeline, and it’s a sure bet that more fossils will turn up. It does make one wonder: what else is hidden beneath the vast expanse of L.A.?