Editor’s Note: Science has transformed our understanding of dinosaurs in the past two decades. Get caught up with what’s new in this five-part CNN series.
Tyrannosaurus rex battled parasites and got gout from its meat-rich diet. Duck-billed hadrosaurs suffered cancerous tumors, and a towering sauropod in China survived a nasty pus-filled infection from a predator bite.
Dinosaurs, like us, got sick and injured. By detecting these medical conditions in fossils, paleopathologists, experts in ancient disease and injuries, are gaining tantalizing insights into dinosaur behavior and evolution – how a dinosaur moved through its world, the relationship between predator and prey, and how dinosaurs of the same species interacted.
Until relatively recently, however, diagnosing multi-million-year-old diseases from fossilized bones was decidedly hit-and-miss.
First off, the fossil record only reveals a small fraction of the creatures that lived in the past, and those that reach us have withstood multiple obstacles over millions of years. What’s more, with soft tissue largely missing from fossils, scientists rely on bones for information. And it’s often very hard to determine whether deformations in a dinosaur’s bone structure were caused by disease or the crush of sediment over time.
Paleontologists can identify strange structures, bone overgrowths, rough surfaces, and holes or porous surfaces in areas where they should not be without the help of special tools. But the application of medical advances like computerized tomography to paleontology have allowed researchers to peer through rock to see what’s happening inside fossilized bones.
“It’s imperative to have an inner view of the bone,” said Filippo Bertozzo, a post-doctoral researcher at the Royal Belgian Institute of Natural Sciences in Brussels. “If you have doubts whether a bone is deformed by pathology or geological processes, you need to see inside.”
“If it’s geology at play, you wouldn’t see any change in the structure of the cells.”
Often it takes a raft of experts in different fields to confirm a diagnosis. Think of an episode of the television series “House” for dinosaurs.
“The study of paleopathologies is more than simply identifying a disease, it is opening a window to learn about interactions with the environment and social behavior,” said Penélope Cruzado-Caballero, a paleontologist at the Research Institute of Palaeobiology and Geology of CONICET, Argentina’s National Council for Scientific and Technical Research, and the National University of Río Negro (Argentina).
For example, paleontologists had long been stumped by the unusual domed skulls of Pachycephalosaurs – small, plant-eating dinosaurs that are bit players in the “Jurassic Park” movie franchise. The discovery of bone lesions resulting from injuries in adults suggested that they used the domes to butt heads – a bit like big-horned sheep do.
Not just big, but tough
The most commonly detected pathology in the dinosaur fossil record is bone fractures – with some dinosaurs apparently surviving very severe trauma that must have left them living in great pain.
Bertozzo has detailed the injuries suffered by one Parasaurolophus walkeri, a dinosaur with a long, curved crest. Its fossil was unearthed in 1921 and has been on display at the Royal Ontario Museum in Toronto for decades.
For years, paleontologists had thought a V-shape indentation in the dinosaur’s spine was part of its natural posture – perhaps to accommodate its long, dramatic headgear.
A new analysis published in 2020 found that the dent was due to a broken back. The creature also had broken ribs, a deformed pelvis and a dental lesion. Bertozzo believes the broken back was possibly caused by a falling rock or tree, but the dinosaur didn’t die of its injuries – at least not immediately. Bertozzo said it would have lived at least four months, and their analysis suggested the injuries had begun to heal before the creature’s death.
Bertozzo believes that some dinosaurs must have been able to overcome and survive massive injuries. He said one hypothesis is that a strong immune system was a survival mechanism for some herbivores, like Hadrosaurs, which didn’t have defensive features like armored plates, spiked tails or sharp horns common in other plant-eating species, such as Triceratops.
Dinosaurs also lived with cancer – in some cases the same form that afflicts humans today. A horned dinosaur called Centrosaurus apertus that lived 76 to 77 million years ago in what’s now Alberta, Canada, was diagnosed in a study published in 2020 with osteosarcoma – an aggressive malignant bone cancer that can affect humans.
Researchers concluded it was an advanced stage of cancer that may have spread throughout the dinosaur’s body. But what might have been a death sentence for one dinosaur, another could endure.
Cruzado-Caballero diagnosed the same cancer in Bonapartesaurus, unearthed in Argentinean Patagonia in the 1980s. This dinosaur had a large cauliflower-like overgrowth of bone on its foot but, she said the growth hadn’t spread to other parts of the animal’s body, and she didn’t think it would have seriously affected its day-to-day life. Likely more painful were two fractures in its tail, which healed in