Theropods (bipedal predatory dinosaurs) may have suffered from bone diseases caused by conditions such as arthritis or congenital malformations, suggests an analysis of three specimens from three different species of South American theropods known as abelisaurids. The findings, published in BMC Ecology & Evolution, provides novel evidence of pathologies not caused by injuries in theropods, and also suggest that different types of theropods may have been prone to different injuries and conditions due to their differing lifestyles.

Mattia A. Baiano and colleagues used CT scans and bone histology analysis to examine three sets of remains of the theropods Aucasaurus garridoi, Elemgasem nubilus, and Quilmesaurus curriei, which all lived in South America during the Late Cretaceous (approximately 90 to 70 million years ago). All three species belong to the abelisaurid family of theropods, which typically have extremely short forelimbs, and deep and powerful skulls that often feature bony ornaments.

The CT scans reveal two fused vertebrae near the base of the tail in the A. garridoi remains that lack common pathological signs such as bone spurs (osteophytes) or lesions. The authors therefore suggest that this fusion was a congenital disorder that developed prior to the individual hatching. The E. nubilus specimen also displayed pathology in two sets of vertebrae in the middle and towards the tip of its tail, with several vertebrae partially fused to each other and evidence of bone overgrowth. The authors propose that this might be a case of inflammatory arthritis. Finally, the authors noted evidence of irregular bone formation in the tibia bone in the Q. curriei specimen, a rare indication of disease in a weight-bearing bone in a theropod. The authors rule out infection but are unable to conclusively identify what the underlying cause might have been.

The authors also reviewed the literature on pathologies in theropods and found patterns of associations between different types of theropods and different injuries and diseases. Abelisauridae theropods had positive associations for bone inflammation (osteomyelitis), which suggests that infections were relatively common in these species. Tyrannosauridae remains were negatively associated with fractures but positively associated with bite marks on the skull, suggesting that these species engaged in aggressive behaviour such as fighting. However, the converse relationship was observed in Allosauridae remains, with the high proportion of fractures suggesting an active predatory lifestyle.

Together, these findings provide insights into the diseases and injuries different theropods were exposed to.

-ENDS-

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Notes to editor:

1. Research article:

“New information on paleopathologies in non‑avian theropod dinosaurs: a case study on South American abelisaurids”
BMC Medicine 2024
DOI: 10.1186/s12862-023-02187-x
The article is available at the journal website.

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