Mosasaur Feeding Ecology from the Campanian Bearpaw Formation, Alberta, Canada: A Preliminary Multi-Proxy Approach

Mosasaur taxa recovered from the Bearpaw Formation, Alberta, Canada, generally show exceptional preservation after rapid burial. Since the mosasaur community consisted of two dominant taxa, Mosasaurus missourensis Prognathodon overtoni, and three less prevalent taxa Tylosaurus proriger, Mosasaurus conodon, and Plioplatecarpus primaevus, some form of habitat or dietary niche partitioning is to be expected. To test this, several approaches are tried. Two-dimensional microwear analysis is used as an exploratory method to quantify tooth abrasion by food items. The good preservation of skull material reveals complete tooth rows of the upper and lower jaws for Mosasaurus missouriensis and Prognathodon overtoni, as well as isolated teeth for all taxa. The teeth are also measured for tooth bending strength to test stress regarding usage of teeth per taxon. Energy-dispersive X-ray spectroscopy (EDX) measurements show trace elements which may be a preliminary test for relative trophic level positioning. Some mosasaurs have their stomach contents preserved, providing direct and unambiguous evidence of diet. The results show a relatively clear separation of two-dimensional microwear counts between Mosasaurus, Prognathodon, and Plioplatecarpus, which, to some extent, is reflected in the EDX analyses, too. Tooth bending strength measurements show a clear difference between the latter three mosasaurs but no difference between the lower and upper jaws in Mosasaurus or Prognathodon. The combination of these three techniques maps a clear dietary niche differentiation of Bearpaw mosasaurs, which lays the groundwork for future analytical or chemical palaeoecological studies.