Dinosaurs faced threats far smaller than an asteroid long before their extinction. A new study reveals that some of South America's largest dinosaurs had deadly bone infections. These infections occurred nearly 80 million years ago.
Researchers studied six long-necked sauropod skeletons from Brazil. They identified signs of osteomyelitis. It is a destructive bone disease still seen today in mammals, birds, and reptiles.
This infection, caused by bacteria, fungi, viruses, or parasites, damages bone tissue and can be fatal if left untreated. The newly examined fossils show that dinosaurs, despite their massive size, were not immune.
The Wetlands That Fostered Pathogens
The fossils were collected at the "Vaca Morta" site in São Paulo state between 2006 and 2023. During the Late Cretaceous, this region was a network of shallow rivers and stagnant pools -- environments ideal for pathogens and disease-carrying organisms.
Sauropods, which preferred floodplains and swamps, may have been especially vulnerable to these infections. Their fossils and footprints often appear in such wetland deposits.
Signs of Active, Fatal Infections
Lead author and paleontologist Tito Aureliano from the Regional University of Cariri (URCA) explained that the fossilized bones showed lesions consistent with fast-progressing infections.
None of the lesions displayed healing, suggesting the infections were active when the dinosaurs died. In some cases, the disease may have directly contributed to their deaths.
The bone damage appeared irregular compared to bite marks, with a "chaotic architecture." Early-stage cases showed lesions inside the bone, while advanced infections left bump-like protrusions on the outer surface.
Insights Into Dinosaur Health
Few examples of infectious disease have been identified in sauropods, making this discovery an important step in understanding dinosaur paleopathology.
Because the infected fossils come from the same site and close time period, researchers believe local environmental conditions may have triggered outbreaks affecting multiple individuals.
The findings highlight that even giant dinosaurs were vulnerable to microscopic enemies that thrived in their habitats.
Dinosaurs may have dominated Earth for millions of years, but this study reveals they faced threats not only from predators and changing climates, but also from pathogens too small to see. For sauropods in prehistoric Brazil, bone infections like osteomyelitis may have been a hidden but deadly danger -- long before the asteroid impact that marked the end of the Cretaceous.