Time Scavengers

Palaeoepidemiology in extinct vertebrate populations: factors influencing skeletal health in Jurassic marine reptiles

Judith M. Pardo-Pérez, Benjamin Kear, and Erin E. Maxwell

Summarized by: Kailey McCain

What data were used? Researchers wanted to create a baseline for measuring overall health of large marine animals in the Jurassic period. Given the prevalence of Ichthyosauria, a large extinct marine reptile, researchers chose to survey five different species/taxa (i.e., biological classification of organisms) that lived at different ocean depths and varied in size: Hauffiopteryx, Stenopterygius, Suevoleviathan, Eurhinosaurus, and Temnodontosaurus.

A total 236 specimens were collected at a Lagerstätte deposit in Germany, which is a site with exceptional (in quantity or quality) fossil preservation.

Methods: The 236 specimens were classified by species, and then further classified by age range (i.e., juvenile, young adult, adult). Researchers began studying the fossils for signs of trauma that could have resulted from injury or skeletal diseases (pathologies). Due to the large availability of the Stenopterygius specimens, researchers dated and grouped them into three categories regarding the Toarcian Oceanic Anoxic Event (T-OAE). This was a time in the Jurassic Period when the oxygen levels were depleted and toxic greenhouse gases (e.g., carbon dioxide and hydrogen sulfide) became the major component of the atmosphere; the specimens were grouped as before T-OAE, during  T-OAE, and after T-OAE. The purpose behind comparing pathological data to the T-OAE is to determine if the depletion of oxygen had any significant effect on marine health.

All of the data was inputted into a statistical software, R, to determine any significant correlations and variables. 

Results: The data collected showed that trauma associated with healing was the most common pathology recorded; however, there was not a skeletal region significantly affected more than the others. These commonalities were shared by all five taxa of ichthyosaurs . Additionally, when comparing the overall size of the specimens and percentage of pathologies found, it was determined that the large species were approximately 2.4 times more likely to show signs of trauma and disease. This correlation was also found to be true when looking at the developmental data collected for Stenopteryguis; it was concluded that the adults were 4 times more likely to have signs of disease or trauma than the juvenile specimens.Regarding the data collected for the Toarcian Oceanic Anoxic Event , researchers could not find any significant data that could correlate an increase in pathologies due to the depletion of oxygen.

Why is this study important? This study showed the differences in skeletal pathologies present in a diverse set of marine reptiles. By differing in size, age, time, and ocean depth, researchers were able to obtain an overall survey of health and easily compare the pathology data to other ecological conditions (e.g., climate change).

The big picture: The research collected in this study provided a baseline for variables that affected the skeletal health of Jurassic marine reptiles. The data supporting the correlations between size and age range of different taxa within the extinct Ichthyosauria can be compared to other extant (i.e., living) reptiles to provide an estimation and a possible explanation for the prevalence of skeletal pathologies.

Citation: Palaeoepidemiology in extinct vertebrate populations: factors influencing skeletal health in Jurassic marine reptiles. (2019). Royal Society Open Science, 6(7). https://doi.org/10.1098/rsos.190264