WHEN WERE WHAT DINOSAURS SICK? A REVIEW OF THE RECORD OF DINOSAUR PALEOPATHOLOGY

Like all living creatures, dinosaurs suffered from a wide range of illnesses. Tangible evidence of these maladies lies in the fossil record, where appropriately preserved specimens can indicate paleopathologies. Studying dinosaur paleopathology can also yield evidence of behavior, as pathological trends with respect to time and clade can test previous assumptions about dinosaur paleobiology. We searched a published compilation of dinosaur paleopathologies (New Mex. Mus. Nat. Hist. Bull. 20, 2002) and consolidated results into a database sorting each record by epoch (Late Triassic, Early Jurassic, etc.) and major clade (Sauropoda, Theropoda, Ornithopoda, Thyreophora, or Marginocephalia). Thus far, no studies describing dinosaur paleopathology as it relates to time period have been published.

Our analysis shows that the record of injuries in theropods is greater than that of any other clade; supporting the hypotheses that theropods were the most aggressive dinosaurs and that predatory lifestyles are dangerous. Thyreophorans have the fewest pathologies, suggesting that their armor and herbivorous nature kept them in the best health. Previous studies have shown that the number of dinosaurian genera increases chronologically, from the Late Triassic to the Late Cretaceous. Records of dinosaur pathology follow this trend except for a “spike” in the Late Jurassic that probably reflects the many dinosaur specimens known from the Morrison Formation. Records of pathology in the Late Cretaceous greatly outnumber any preceding time period, but may be skewed by the antagonistic behavior of dinosaurs extant during that time, such as ceratopsians, notorious for intraspecific fighting, and large theropods that are more susceptible to injury due to their predatory nature and the defense mechanisms of their prey. Future directions include a more detailed breakdown by stage-age and a critical analysis of the records in the compilation to test the explanations advanced here.