Fossil Species discrimination: Mesodma

 A lower fourth premolar of  Mesodma thompsoni .

A lower fourth premolar of Mesodma thompsoni.

The mammalian fossil record is largely composed of isolated teeth and tooth-bearing elements. In vertebrate microfossil assemblages with closely related, co-occurring species of mammals, it can be difficult to identify isolated teeth to species level because morphological differences among species may be slight and based on a single tooth position. In collaboration with my advisor (Dr. Greg Wilson), I investigated the utility of the allegedly diagnostic lower fourth premolar (p4) for species-level identification in the genus Mesodma (Multituberculata, Neoplagiaulacidae).

Our results indicate that size is more important than shape in determining species-level identification of these teeth, and that at least one species undergoes anagenetic over the Cretaceous-Paleogene mass extinction boundary.

Smith, S. M., and Wilson, G.P. 2016. “Species discrimination of co-occurring small fossil mammals: A case study of the Cretaceous-Paleogene multituberculate genus Mesodma.” Journal of Mammalian Evolution 24: 147–157. doi: 10.1007/s10914-016-9332-2