In 1989, scientists first unearthed fossils of a horned dinosaur called Centrosaurus in the badlands of Dinosaur Provincial Park in Canada’s Alberta province. During their research, they found it had a badly malformed leg bone they thought was a healed fracture.

But a new examination of the bone shows something different, researchers said on Monday.

The malformation in the bone was a manifestation of osteosarcoma, which is an aggressive bone cancer, making the Centrosaurus, which lived 76 million years ago, the first dinosaur afflicted by a malignant cancer.

Centrosaurus was a four-legged beaked plant-eating Cretaceous Period dinosaur that is about 20 feet (six meters) long, had a long horn above its nose and a bony frill above its neck with two smaller hooked horns.

“[The Centrosaurus fibula, a lower leg bone, contained] a massive gnarly tumor larger than an apple,” paleontologist David Evans of the Royal Ontario Museum in Toronto, one of the researchers in the study published in the journal Lancet Oncology, told Reuters in an interview.

“This particular Centrosaurus was likely weak and lamed by the cancer prior to its death. This remarkable find shows that no matter how big or powerful some dinosaurs may seem, they were affected by many of the same diseases we see in humans and other animals today, including cancer. Dinosaurs seem like mythical beasts, but they were living, breathing animals that suffered horrible injuries and diseases,” he added.

The researchers confirmed the malformation was a tumor using high-resolution CT scans and by looking at thin sections under the microscope.

“We were not only able to demonstrate that the bone tissue showed the hallmarks of osteosarcoma, but that the tumor spiraled through the cortex of bone, discounting its original identification of a healed fracture,” said Evans.

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