The femur of a 240-million-year-old reptile found this month in Germany may be one of the oldest cases of cancer ever discovered—and cancer researchers are clamoring to study the ancient fossil, The New York Times reports.

The major paleontological find, written about last week in JAMA Oncology, describes the cancerous leg bone of a Pappochelys (a shell-less ancestor of turtles) as the earliest-known case of cancer in an amniote, an animal group that includes reptiles, birds and mammals. Cancer seldom appears in the fossil record—and never this far back, say researchers.

The leg bone was discovered in an ancient lake bed, where its jagged growth drew the eyes of scientists at the Stuttgart State Museum of Natural History and later the Natural History Museum, Berlin, reports the Times. After taking micro-CT scans of the femur, they identified the swelling as an osteosarcoma, a type of bone cancer also found in humans.

Until recently, the lack of evidence for prehistoric cancer had led some researchers to theorize that the disease is a modern phenomenon, linked to ill health, pollution and increased life spans, but this finding challenges that notion.

“What makes this really cool is that now we understand that cancer is basically a deeply rooted switch that can be turned on or off,” said Yara Haridy, MS, a paleontologist at the Natural History Museum in Berlin, who was on the team of scientists that identified the ancient cancer. “It’s not something that happened recently in our evolution. It’s not something that happened early in human history, or even in mammal history.”

This isn’t the first time that the ancient animal world has given humans clues to the origins of cancer. In 2001, a team of Russian scientists identified a possible osteosarcoma in an Early Triassic amphibian. In 2016, a similar study identified a benign jaw tumor on a 255-million-year-old pre-mammal.

To learn more about cancer in animals and what it can tell us about modern-day treatment, click here.