October 8, 2016:

by Lorrie McWhinney and Angela (Angie) Matthias

This study slowly developed and changed over 17 years. The discovery of “Lorrie’s Site” in 1999 was a byproductof prospecting for eggshell material for Darla Zelenitsky, then a PhD student from Canada, who is now an Assistant Professor at the University of Calgary. At that time, Dr. Ken Carpenter (director and curator of paleontology at Utah State University Eastern Prehistoric Museum, in Price, Utah) had two sets of volunteer teams prospect in the Cedar Mountain Formation. My co-author, Angie, and Brenda Johnson went in one direction, while Darla Zelenitsky and I (Lorrie) headed toward an exposed area of the Ruby Ranch member of the Cedar Mountain Formation. No egg shell, but Darla and I found bone fragments littering the ground. Darla decided to search another area for eggshell while I stayed behind. Since I was prepared to find tiny eggshell fragments, I didn’t bring anything bigger to put larger specimens in for collection. Therefore I selected a few specimens and held them in my hand as I continued prospecting for eggshell material. When both teams returned, Dr. Carpenter asked about our findings. No one had found fossil eggshells. However, since I had collected some of the bone fragments, I handed him my findings. Dr. Carpenter instantly recognized what I had found: ankylosaur armor fossils called osteoderms. He asked me to name the site. I said that the name could be the ‘Lady Luck Site’ – I wanted to credit both Darla and me. Unfortunately, this name was overruled and “Lorrie’s Site” stuck instead.

The preparation process in the lab revealed that numerous ankylosaur armor samples appeared pathological. With the encouragement of Dr. Carpenter, I was given the opportunity to investigate why we were finding “pitting” on the exterior of the bone. I used to work for Kaiser Permanente, and so I had a lot of disease resources available to me. It soon became apparent that more samples were needed for a proper investigation. Each subsequent field season increased the number of pathological specimens. After Angie joined me in this investigation, we looked at other museum collections, interviewed many professionals in different fields of expertise, and reviewed endless amounts of publications. Despite the fact that pitting or cratering on ankylosaur osteoderms has been noted by various authors, our study was the first detailed analysis of such pits based on a large sample size of osteoderms. We ended up examining over 1100 osteoderms that exhibited a peculiar pitting with different shapes and sizes. Data on the pits were collected with digital calipers, thin-section analysis, SEM, and non-destructive X-ray computed tomography. The comparative data on pitting in modern relatives, such as crocodiles, was collected from veterinarians as well as from observations of recently-dead alligators.

References:

Appleby, J., Thomas, R., Buikstra, J., 2015. Increasing confidence in paleopathological diagnosis–Application of the Istanbul terminological framework. International Journal of Paleopathology, 8, 19–21.

To learn more:

Matthias, A. E., McWhinney, L. A., & Carpenter, K. (2016) Pathological Pitting in Ankylosaur (Dinosauria) Osteroderms. International Journal of Paleopathology, 13, 82-90. http://dx.doi.org/10.1016/j.ijpp.2016.02.006