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).
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.
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.
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.
Starving T. rex
T. rex was the ultimate dinosaur predator, weighing as much as two African elephants, but it could fall victim to the tiniest of foes: parasites.
The lower jaw of SUE the T. rex, the most complete T. rex skeleton ever found, was pitted with smooth-edged holes. Initially experts thought they were bite marks or a bone infection, but researchers ultimately concluded the holes were a result of a parasitic infection called trichomonosis. The condition can also effect the lower jaw of modern birds like pigeons, doves and chickens.
“Once the animal was infected, feeding would have been difficult, and it is highly likely that, as seen in living birds, the mighty tyranosaurs lost considerable weight before eventually starving to death.”
Could dinosaurs have been attacked by coronaviruses?
“Birds, especially pet birds, do suffer from pulmonary infection. Birds are dinosaurs, and dinosaurs presented, most likely, a birdlike lung system,” Bertozzo said. “I would expect dinosaurs to suffer from similar pulmonary infections as in birds. Of course, Covid is a novel disease, we cannot know if something similar happened in the past, so we can’t say if dinosaurs suffered from Covid-like diseases.”
Bertozzo is building a database to record incidences of trauma and disease across different species of ornithopods — a family of plant-eating dinosaurs that includes iguanadons, hadrosaurs and duck-billed dinosaurs — and across different time periods. He hopes it will help answer questions like which group of these dinosaurs was most likely to suffer disease and whether these conditions affected dinosaur behavior.
“It’s a growing field that is going to give us a lot information about the lives of these fascinating creatures,” he said.