A dinosaur that died around 76 million years ago had an aggressive, malignant cancer that would have been "crippling" for the animal, researchers have found.
This is the first time scientists have identified the presence of a malignant cancer—one that can spread to other parts of the body—in a dinosaur, according to a study published in the journal The Lancet Oncology.
The dinosaur in question lived around 77 million to 76 million years ago in what is now Canada. It belonged to the species Centrosaurus apertus—a type of horned, herbivorous, quadrupedal dinosaur that measured up to around 18 feet in length.
The remains of this particular dinosaur were first uncovered in 1989 in Dinosaur Provincial Park, Alberta. At the time, paleontologists noticed that one of the specimen's lower leg bones—the fibula—was badly deformed, something they thought was the result of a healing fracture.
However, after noticing the unusual characteristics of the bone during a trip to the Royal Tyrrell Museum in 2017, another team of scientists from the Royal Ontario Museum (ROM) and McMaster University decided to examine the fossil further using modern medical techniques, including high-resolution CT scans.
From this analysis, the team concluded that the dinosaur suffered from an aggressive and advanced malignant bone cancer, known as osteosarcoma, in the fibula, which can explain the strange deformations.
"Diagnosis of aggressive cancer like this in dinosaurs has been elusive and requires medical expertise and multiple levels of analysis to properly identify," Mark Crowther, Professor of Pathology and Molecular Medicine, and an author of the study from ROM, said in a statement. "Here, we show the unmistakable signature of advanced bone cancer in 76-million-year-old horned dinosaur—the first of its kind. It's very exciting."
Osteosarcoma is a type of cancer that originates in the cells that form bones. It is most commonly diagnosed in long bones, such as those of the leg, although it can occur in any part of the skeleton.
"The shin bone shows aggressive cancer at an advanced stage. The cancer would have had crippling effects on the individual and made it very vulnerable to the formidable tyrannosaur predators of the time," said Evans.
"The fact that this plant-eating dinosaur lived in a large, protective herd may have allowed it to survive longer than it normally would have with such a devastating disease," David Evans, a paleontologist from ROM and another author of the study, said in a statement.
Despite the osteosarcoma diagnosis, however, it appears that the dinosaur may have died in a flood, along with a large herd of centrosauri.
"We know that the specimen was found in a bonebed, which is a large collection of fossils from many individuals of the same species, suggesting a mass death event, such as flooding. This suggests that the individual was still keeping up with the herd when they died, even if they were not moving at full speed," Seper Ekhtiari, another author of the study from McMaster University, told Newsweek.
"Centrosaurus herds numbered in the thousands, so even if this individual was moving more slowly than normal, it is quite possible that they could have been sheltered by the herd. Very young and elderly individuals are often sheltered in a similar manner in the herds of large herbivorous animals. However, it is difficult to know for sure whether the dinosaur died from the flooding or from the spread of the cancer itself, as the two events could have occurred around the same time, leading to similar findings."
According to the researchers, the latest paper highlights several important issues, including the importance of multidisciplinary collaboration.
"In medicine, multidisciplinary teams are extremely valuable and critical to patient care," Ekhtiari said. "Most of our patients are seen not only by doctors from different specialties, but also by a range of other healthcare professionals, including nurses, physiotherapists, occupational therapists, and many more."
"Similarly, this first-time diagnosis of a malignant cancer in a dinosaur required a truly collaborative effort from paleontology, orthopedic surgery, engineering, pathology, imaging scientists, and many more. Moving forward, this type of collaborative expertise, along with the use of modern technology, can help to solve further ancient mysteries hidden in both new and previously discovered fossils."
Furthermore, the study also highlights the common underlying biology of cancer, an affliction that affects all manner of organisms.
"We see osteosarcoma most commonly in adolescents and young adults, and this is thought to be because that is when our bones are growing most quickly, creating an environment that is ripe for abnormal bone growth, such as osteosarcoma," Ekhtiari said.
"We also know that one of the ways dinosaurs reached their enormous sizes was through extremely rapid bone growth. Thus, it is perhaps not surprising to see this diagnosis made in a dinosaur, and it is very likely that the underlying biology of osteosarcoma, and cancer in general, has been quite similar throughout its history, a history which extends back much further than humans have been around."
This article was updated to include additional comments from Seper Ekhtiari.
