A slab of rock at an Australian high school, a boulder in a parking lot, and a bookend in a private collection feature 200-million-year-old dinosaur footprints.

Dozens of dinosaur footprints embedded in a boulder were found hiding in plain sight at an Australian school, according to researchers.

For two decades, students walked past an unassuming beige rock on their way to and from class—and occasionally stuck wads of used chewing gum on it. Now, paleontologists have discovered the slab is covered in 200-million-year-old dinosaur tracks,