Fossils suggest dinosaurs could get ill from respiratory disease

Could Brontosaurus get bronchitis and Coelophysis contract a cold? New research suggests that dinosaurs may have been vulnerable to airborne diseases. 

Researchers in the USA and Canada examining the bones of a young diplodocid dinosaur, nicknamed Dolly, found that even some of the largest animals to walk the Earth weren't immune to respiratory illness.  

The fossils of the long-necked sauropod, found in Montana, showed unusual lesions which have been interpreted as evidence of airsacculitis, an inflammatory disease caused by infection that still affects birds today.  

Lead author Dr Cary Woodruff, says, 'Given the likely symptoms this animal suffered from, you can't help but feel sorry for Dolly when you're holding these infected bones in your hands.  

'We've all experienced these same symptoms – coughing, trouble breathing, a fever – and here's a 150-million-year-old dinosaur that likely felt as miserable as we all do when we're sick.' 

Though it can't be confirmed, the researchers speculate that the disease could have been caused by a severe fungal infection, similar to aspergillosis. Understanding the diseases that affected the dinosaurs can give scientists a better idea of how today's illnesses evolved, providing new options for fighting them. 

What diseases affected dinosaurs?

Our knowledge of dinosaurs comes from a variety of sources. In addition to bones, preserved dinosaur footprints, poo and even skin can be used to work out what the extinct animals looked like and how they could have behaved. 

Scientists can also make inferences from modern birds, who are descended from the dinosaurs. Bird genetics, skeletons and behaviour can give clues about their ancient relatives 66 million years after the latter's extinction. 

The study of diseases that affected dinosaurs, however, is harder to assess. While internal organs can sometimes be preserved in fossils, this only occurs very rarely. Instead, most knowledge of dinosaur illness comes from when a disease affects the bone. 

In 2020 the fossils of a Triceratops relative, Centrosaurus apertus, showed that dinosaurs could contract bone cancer. This built on previous finds which demonstrated the animals could develop neoplasia, or uncontrolled cell growth.

Following on from this, the leg bone of a Brazilian titanosaur was found to contain fossilised parasites, offering a look at how disease-causing organisms behaved in the Cretaceous Period. 

In 2021, a group of Brazilian scientists found some of the first evidence of a respiratory infection in an aeolosaurinid titanosaur, whose rib bone showed evidence of pneumonia, possibly from a tuberculosis infection.  

However, the structure of the bone showed similarities to medullary bone, a structure that forms in female birds when they are ready to lay eggs. While the presence of medullary bone in dinosaurs is still debated, it makes it difficult to know conclusively whether or not this titanosaur was suffering from pneumonia. 

What symptoms did dinosaur respiratory disease cause? 

The fossils of Dolly, consisting of a skull and parts of the neck, was uncovered from the Morrison Formation in the USA. Many famous dinosaur species have been described from these rocks including Diplodocus carnegii, the species of dinosaur represented by the Museum's Dippy cast. 

While Dolly's exact species is not known, it is believed to belong to the diplodocidae, which include dinosaurs such as Diplodocus, Apatosaurus and Brontosaurus. These dinosaurs are believed to have used a breathing system similar to that found in modern birds, with air sacs and hollow bones that allowed them to absorb oxygen while inhaling and exhaling. 

When examining Dolly's vertebrae, the scientists noticed damage in areas of the bone linked to breathing. The lesions did not appear to be associated with fossilisation, as the damage didn't extend beyond these pneumatic bone structures. 

As the bones showed no signs of healing, this led the researchers to believe the abnormal structure was associated with a chronic respiratory disease. They narrowed down the list of possible causes to three options, including neoplasia, airsacculitis or pneumoconiosis, a disease caused by breathing in significant amounts of dust or other particles. 

Of these, they believe that airsacculitis is the most likely cause. Evidence of neoplasia would likely have extended beyond the pneumatic bone structures, while there is limited evidence of events such as volcanic eruptions that would have caused pneumoconiosis. 

In particular, they speculate that the air sac infection may have been caused by a fungus like Aspergillus, which thrives in humid environments such as those likely to have existed in ancient Montana. Furthermore, Aspergillus spores are known to date back around 50 million years, although this is still 100 million years short of when Dolly was alive. 

As Dolly was still a juvenile when they died, it is possible that the infection may have been the cause of death.  

Beyond confirming the presence of respiratory disease, this specimen helps palaeontologists to better understand how dinosaurs breathed, as well as the evolution of diseases which still affect animals today. 

Cary says, 'This fossil infection in Dolly not only helps us trace the evolutionary history of respiratory-related diseases back in time, but gives us a better understanding of what kinds of diseases dinosaurs were susceptible to.'