A PRELIMINARY STUDY OF DINOSAUR ILLNESS AND INJURY THROUGH THE MESOZOIC: A POSSIBLE CASE OF NORTH AMERICAN BIAS?

We evaluated instances of dinosaur illness and injury over geologic time through a comprehensive review of records of dinosaur paleopathology. Our aim was to test the hypothesis that, as dinosaurs diversified and increased in numbers, there would be more incidents of pathology in the fossil record. A published compilation of paleopathologies was reexamined and sorted to only use reliable sources and therefore eliminate “bad” data. Examples of “bad” data included any that was not from a peer-reviewed source, that repeated the same specimen in the database, or that represented non-pathologic occurrences. The data was then entered into a database, using fields such as full classification, location, and time interval, and pathologic occurrences over geologic time were plotted to compare to published estimates of dinosaur diversity.

The records of dinosaur paleopathology do not correlate directly with the published dinosaur diversity curve. Pathologic incidents spike in the Late Jurassic, dip in the Early Cretaceous, and spike again in the Late Cretaceous. Upon review we propose that this is due to a regional research bias due to the fact that most of the available paleopathologic records represented North American specimens, with relatively few records from other parts of the world. There was influence in the Late Jurassic data by the Morrison Formation as well as influence in the Late Cretaceous by the many Upper Cretaceous units of the Western Interior. We also note that there was a significant occurrence of large dinosaurs in the data from the Late Jurassic and Late Cretaceous, which would be easier to preserve and may possibly account for a lack of pathologic specimens relative to smaller dinosaurs in the rest of the data.

Our results indicate that large theropods were injured frequently, sauropodomorphs more often incurred conditions related to age or great size, and ornithischians suffered from both injury and illness rather equally, relative to theropods and sauropodomorphs. For the theropods this is probably due to their relatively violent lifestyle. The sauropodomorphs frequently exhibited signs of spinal diseases and arthritis, which is prevalent in many large land animals today. Future work includes attempting to standardize the data overall, with eventual comparison to established databases.