Dinosaur life wasn't all peaches and cream before the Chicxulub asteroid struck Earth. Some were plagued by much smaller dangers long before.
A new study has found evidence that a potentially deadly bone disease endangered the lives of numerous long-necked dinosaurs in what is now Brazil, roughly 80 million years ago.
These are some of South America's largest dinosaurs, and yet they faced a very tiny enemy.
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Scientists have now described the ancient skeletons of six sauropods from Brazil that contain signs of osteomyelitis – a destructive bone infection caused by a bacterium, fungus, virus, or parasite.
Today, the infection impacts mammals, birds, and reptiles.
During the Cretaceous, it may have killed dinosaurs. The ancient home of sauropods in Brazil would have once hosted a network of shallow, slow-moving rivers and large pools of standing water – ripe for pathogens and the creatures that carry them.
For better or worse, sauropods seem to have preferred these wet ecosystems. Their footprints and other fossils are often found in ancient floodplains or swamps.
"There have been few findings of infectious diseases in sauropods, the first having been published recently," says lead author and paleontologist Tito Aureliano from the Regional University of Cariri (URCA) in Brazil.
"The bones we analyzed are very close to each other in time and from the same palaeontological site, which suggests that the region provided conditions for pathogens to infect many individuals during that period."
The precious fossils of unspecified species were collected between 2006 and 2023 at the "Vaca Morta" site in the Brazilian state of Sao Paulo.
Because none of the bone lesions show evidence of healing, the infections were probably still active at the time of death. They may even have contributed.
Based on the disease pathology, Aureliano and colleagues argue that the bone infection advanced quickly. Unlike dinosaur bite marks, the bone lesions possess a "chaotic architecture".
Some sauropod bones only contain lesions on the inside, while others with more advanced infections show circular bump-like protrusions on the outside. The findings suggest that the disease can progress in different ways, maybe depending on the dinosaur or the type of pathogen involved.
Dinosaurs may have once dominated the Earth, but even the tiniest pathogens may have threatened their reign.
The study was published in The Anatomical Record.