An absence of archaeological and palaeontological evidence of pneumonia in the remote past contrasts with its recognition in the more recent archaeologic record. We document an apparent infection-mediated periosteal reaction affecting the dorsal ribs in a Middle Triassic eosauropterygian historically referred to as ‘Proneusticosaurus’ silesiacus. High-resolution X-ray microtomography (XMT) and histological studies of the pathologically-altered ribs revealed the presence of a continuous solid periosteal reaction with multiple superficial blebs (protrusions) on the visceral surfaces of several ribs. Increased vascularization and elevated lines of arrested growth document that the pathology was the result of a multi-seasonal disease. While visceral surface localization of this periosteal reaction represents the earliest identified evidence for pneumonia, the blebs may have an additional implication: they have only been previously recognized in humans with tuberculosis. Parsimonious with this diagnosis is the presence of focal vertebral erosions, another manifestation of tuberculosis in humans.