Dental Structure of the Late Cretaceous (Maastrichtian) Guitarfish (Neoselachii: Batoidea) Myledaphus pustulosus from the Hell Creek Formation of Garfield County, Montana

In this study, we examine surface collected teeth of Myledaphus pustulosus from the Upper Cretaceous (Maastrichtian) Hell Creek Formation of Garfield County, Montana. Macroscopic analysis of teeth shows that 54% of the teeth have pronounced attritional wear due to a durophagous diet. A higher percentage of unworn teeth than worn teeth (64% vs 27%) have acid damage due to predation or scavenging. Ultrastructural analysis of whole and sectioned teeth show that the enameloid of the teeth is 100–125 µm thick and is composed of a single crystallite enameloid in which apatite crystallites show no preferred orientation. Orthodentine in the tooth crown is composed of dense material with numerous canals for odontoblast processes which extend nearly to the tooth surface. Dentinal tubules surround odontoblasts most of the way through the enameloid. The enameloid microstructure of M. pustulosus is consistent with the pattern seen in other batoids.