Abstract

This research documents for the first time the detailed histological description of severe bone inflammation and the exceptional preservation of soft-bodied parasitical microorganisms inside the vascular canals of a non-avian dinosaur. The results bring new insights into the fields of parasitology, pathology, and histology in the fossil record. A senile titanosaur from the Upper Cretaceous of Southeast Brazil presented acute osteomyelitis, identified by the presence of a highly reactive periosteum with a filigree pattern, and localized dome-like cortical tissue inflammation connecting the former to the medulla. Furthermore, tens of parasites were identified throughout the specimen’s vascular canals. Novel histological insights resulted from the developmental description of an aggressive case of osteomyelitis. The lesions were either caused or facilitated by the parasitic infestation. This may be the earliest occurrence of infectious bone disease associated with parasites, adding new information to the complex biogeographic and evolutionary history of parasitic ailments.