Patterns of paravertebral ossification in the prehistoric saber-toothed cat.

In cases of paravertebral ossification in humans, the radiographic characteristics usually lead to a specific diagnosis. Similar manifestations are sometimes described in other species. We applied knowledge of the radiographic appearance of spinal alterations in modern humans to the evaluation of 48 fused thoracic and lumbar fossilized spine specimens from the prehistoric saber-toothed cat (Smilodon californicus), in which prominent paravertebral ossification is frequently found. Inspection, conventional radiography, and, in some cases, CT and fluoride analyses were performed. The spinal alterations in the saber-toothed cat, which previously were believed to be caused primarily by trauma, showed characteristics of three major pathologic processes: trauma, diffuse idiopathic skeletal hyperostosis, and inflammatory disease of a type similar to ankylosing spondylitis. The last two categories have rarely been diagnosed in species other than humans. The results suggest that diffuse idiopathic skeletal hyperostosis and inflammatory spondyloarthropathy are diseases that occurred in prehistoric times and are not confined to the human species.