This project will investigate the chewing behavior of a poorly understood fossil mammal from the epoch immediately following the extinction of the non-avian dinosaurs. Modern mammals chew in a distinctive sideways pattern that is an important part of their adaptation to high metabolism lifestyles. Mammals of the early Cenozoic era, which began about 65 million years ago, may have had a wider variety of adaptations, potentially including heavy reliance on vertical chewing, as seen in most reptiles. This may have accompanied an arrangement of the cusps of the teeth such that they would wear rapidly into flat crushing surfaces. Alternatively, heavy, planar wear on the teeth of some early Cenozoic mammals may represent a constraint on their ability to evolve solutions to resist wear caused during a normal chewing sequence by grit adhering to food. Because mammals must bring their teeth together into a stereotyped fit during occlusion, the shapes of the teeth can be used to predict the path of the two teeth as they come into alignment, and thus test these alternate hypotheses. Dr. Alistair Evans, the project host at Monash University, is a world expert in the use of digital models to reconstruct chewing path in this manner.
Fossil material of the species under study, Aphronorus orieli, comes from the Paleocene Bangtail Formation of Montana. It includes a complete, occluding jaw and cranium and miscellaneous upper and lower dental material that will be used to supplement the reconstruction as needed. A. orieli is a member of the Family Pentacodontidae, which may be related to living pangolins. The occlusal path of A. orieli will be reconstructed from digital models of the upper and lower dentition and compared to the treeshrew Ptilocercus lowii. P. lowii is a generalized insectivore similar in body size to A. orieli whose chewing behavior can be inferred to occur in a transverse path a priori from studies of its close relatives in the genus Tupaia.
This award, under the East Asia and Pacific Summer Institutes program, supports summer research by a U. S. graduate student and is jointly funded by NSF and the Australian Academy of Science.
