A hundred and forty-five million years ago, one particular sauropod dinosaur must have been downright miserable. Mucus dripping from its nostrils, the Jurassic herbivore suffered a fever and coughs that shook its long, muscular neck. The ailment may have even been deadly; the disease so severely affected the dinosaur’s health that it left visible evidence in its fossilized bones.
These strange remains are now the first evidence of a respiratory infection in a dinosaur, paleontologists propose.
What was ailing the poor sauropod, nicknamed “Dolly,” wasn’t immediately clear to scientists studying the animal’s remains. In 2018 paleontologist Cary Woodruff of the Great Plains Dinosaur Museum in Montana was investigating this Diplodocus-like herbivore when he noticed something strange. In the hollows of the dinosaur’s neck bones were outgrowths that looked almost like broccoli.
“I’ve looked at a lot of sauropod vertebrae, and I’ve seen some weird things, but never anything like these structures,” Woodruff says.
Woodruff posted photos to social media and quickly got responses from researchers who recognized that the structures were similar to growths seen in living birds and other reptiles. Some of those scientists joined Woodruff in studying the fossils, which show signs of a disease in the dinosaur’s lungs, the team concludes in a new paper in the journal Scientific Reports.
“Disease in all of its forms has been with animals since the beginning of their evolution,” says Ewan Wolff, a study co-author and paleopathologist at the Museum of the Rockies in Montana.
Fossils like Dolly thus allow experts to track the evolution of modern ailments. (Also read about fossils showing that a T. rex was infected with parasites.)
“Specimens such as this can help shed light on what sorts of diseases were affecting dinosaurs millions of years ago,” says University of Wisconsin Oshkosh paleontologist Joseph Peterson, who was not part of the study team.
Diagnosing a dinosaur disease isn’t easy, especially when the patient has been dead for nearly 150 million years. There are many different diseases that can cause respiratory infections, so the scientists had to narrow down the possibilities.
Tools like x-rays, CT scans, and thin sections of bone can reveal the fossils’ microstructure and add critical information. But the main evidence that this dinosaur had a respiratory infection comes from comparing its bones to those of other animals.
Birds are living dinosaurs, and crocodiles are the closest living relatives to dinosaurs as a group, Wolff notes, so diseases or immune responses shared between them were probably relevant to non-avian dinosaurs like Dolly, too. Sauropods like Dolly also had a complex system of air sacs in and around their bones as part of their respiratory systems, just as modern birds do.
Based upon their study of Dolly and other organisms, Woodruff, Wolff, and colleagues propose that the most likely culprit is a pneumonia-like ailment known as airsacculitis. Rather than being a specific virus or pathogen, airsacculitis describes the inflammation or infection of the air sacs, which might be caused by bacteria, fungi, or viruses. Modern chickens, for example, can get airsacculitis from E. coli when kept in unsanitary conditions.
“The authors present a strong circumstantial case for airsacculitis,” says Washington State University paleontologist Cynthia Faux, who was not involved in the new study. Definitive diagnosis is difficult, even in living animals, but the way the dinosaur’s bones responded to the disease tracks how living vertebrates react to the same ailment.
“We can apply what we know about extant bone response to disease to prehistoric animals and make logical conclusions,” Faux says.
A rough disease
Based on observations of living birds with airsacculitis, Woodruff and colleagues think that Dolly must have struggled with the illness. “Coughing, breathing difficulties, lethargy, fever, sneezing, and diarrhea—these are all respiratory-derived symptoms expressed in birds today,” Woodruff says.
The disease might have been a death sentence for Dolly. Even though there’s no way to be certain how the dinosaur perished, Woodruff notes that diplodocids such as Dolly likely moved in herds, but an ill animal may have fallen behind or left the group. The disease might have then proven fatal for Dolly of its own accord, or it’s possible that a hungry predator saw the ailing dinosaur as an easy lunch.
Learning more about which dinosaurs suffered from what sorts of illnesses could help scientists understand some previously unseen aspects of dinosaur behavior, Peterson says. (Find out the many ways scientists are reimagining dinosaurs in today's golden age of paleontology.)
One way that airsacculitis is spread in birds, Wolff notes, is in cramped conditions where a high concentration of feces and eggs can spread bacteria and cause the disease. Sauropods like Dolly are known to have nested in colonies, Wolff says, and in some situations airsacculitis might have run rampant in dinosaur nesting grounds.
Dolly’s diseased bones also offer a unique connection to the past. Some maladies in the fossil record—such as healed bite wounds or broken bones—might be hard to relate to, Woodruff says. But respiratory disease is something humans are potently familiar with.
“We’ve all had many of the same symptoms and likely felt just as crappy as Dolly did,” Woodruff says. “I don’t personally know of any fossil I’ve been able to sympathetically relate to more.”