The backbone of a 220-million-year-old crocodile-shaped dinosaur shows clear signs of an inflammatory vertebral condition, scientists at the Berlin Natural History Museum reported in the PLOS One science journal.
They ran the vertebrae through a computer tomography scan, and found three areas which clearly suggested spondyloarthritis - a kind of rheumatic disease which causes arthritis.
This leads to the growth of bone mass between joints, which squashes the soft tissue which is supposed to be there, and in people can lead to curvature of the spine.
The dinosaur in question, a phytosaur, also known in German as a crocodile dinosaur, grew to between three and six metres long, and lived mostly in the water but also on land.
Such bone disease has only rarely been demonstrated in dinosaurs, the scientists said.