Dinosaurs may have been wiped out by the impact of a devastating meteorite strike, but before their cataclysmic extinction they had to deal with the threat of diseases such as those animals and humans have to contend with today, new research suggests.
In particular, a close study of the fossil of a malformed leg bone from one dinosaur has revealed the animal suffered from an aggressive malignant bone cancer before it died.
The fossil from the horned dinosaur Centrosaurus apertus — similar in appearance to the triceratops — was found in Alberta, Canada, in 1989. The species lived 76 to 77 million years ago — around 10 million years before dinosaurs were wiped out.
The misshapen appearance of the fibula, a lower leg bone, was originally attributed to the healing of a fracture, but when scientists looked at the bone again in 2017, they decided to study it in more detail, and brought together a team of specialists and medical professionals from a broad range of fields including pathology, radiology, orthopaedic surgery, and palaeopathology.
The team re-evaluated the bone and said they approached their diagnosis similarly to how it would be done for the diagnosis of an unknown tumour in a human patient.
“Diagnosis of aggressive cancer like this in dinosaurs has been elusive and requires medical expertise and multiple levels of analysis to properly identify,” said Mark Crowther, professor of pathology and molecular medicine at McMaster University.
“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.”
To make the diagnosis, the team carefully examined, documented, and then cast the bone, before performing a high-resolution CT scan on the fibula.
They then thin-sectioned the fossil bone and examined it under a microscope to assess it at the bone-cellular level.
Powerful three-dimensional CT reconstruction tools were used to visualise the progression of the cancer through the bone. Using this rigorous process, the investigators reached a diagnosis of osteosarcoma.
To confirm this diagnosis, they then compared the fossil to a normal fibula from a dinosaur of the same species, as well as to a human fibula with a confirmed case of osteosarcoma.
The fossil specimen is from an adult dinosaur with an advanced stage of cancer that may have invaded other body systems, the scientists said.
But despite the diagnosis, it appears the cancer was not what killed this individual. The fossil was found in a massive bonebed, suggesting it died as part of a large herd of centrosaurus struck down by a flood.
“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 Dr David Evans of the Royal Ontario Museum, an expert on these horned dinosaurs.
“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.”
Osteosarcoma is a bone cancer that usually occurs in the second or third decade of life. It is an overgrowth of disorganised bone, which rapidly spreads both through the bone in which it originates and to other organs, including most commonly, the lung.
“It is both fascinating and inspiring to see a similar multidisciplinary effort that we use in diagnosing and treating osteosarcoma in our patients leading to the first diagnosis of osteosarcoma in a dinosaur,“ said Seper Ekhtiari, an orthopaedic surgery resident at McMaster University.
“This discovery reminds us of the common biological links throughout the animal kingdom and reinforces the theory that osteosarcoma tends to affect bones when and where they are growing most rapidly.”
The team said their study aims to establish a new standard for the diagnosis of unclear diseases in dinosaur fossils and opens the door to more precise and more certain diagnoses.
They said establishing links between human disease and the diseases of the past will help scientists to gain a better understanding of the evolution and genetics of various diseases.
The scientists said “evidence of many other diseases that we share with dinosaurs and other extinct animals may yet be sitting in museum collections in need of re-examination using modern analytical techniques.”
The research is published in the journal Lancet Oncology.