The Microsyopidae, a family of plesiadapiforms known from over 1,500 stratigraphically controlled specimens from the southern Bighorn Basin of Wyoming, span the first three million years of the early Eocene. The early Eocene is characterized by rapid fluctuations in climate during the period represented by this collection of microsyopids, making this an ideal sample to examine how climate influenced early stem primate biology, particularly dietary ecology. An evolving lineage of microsyopine microsyopids is known from before, during, and after Biohorizon A, a faunal turnover event associated with a period of localized cooling. Dental topographic analysis (DTA) quantifies functional aspects of molars such as curvature, complexity, and relief, and covaries with diet in extant taxa. Here, we use DTA to examine microsyopid dietary change over time, particularity in response to this cooling event. Our results suggest that microsyopids had molars that are functionally like extant insectivorous/ omnivorous euarchontans. The earliest occurring species in our sample, Arctodontomys wilsoni, is characterized by molars that became more like modern insectivorous euarchontans over time. During Biohorizon A, A. wilsoni is replaced by A. nuptus, which has molars that are more like those of extant omnivores with a mixed diet including fruit. After the biohorizon event, A. nuptus appears more insectivorous, as is the later occurring Microsyops angustidens, which evolves from A. nuptus. Overall, we provide potential evidence for a causal scenario where local climate change coincided with a dietary transition among microsyopids. Our results have important implications for understanding how diet and climate were prime movers for the evolution of early primates.

These are dental topographic data collected from micro-CT scans and measured using MorphoTester, as well as body mass estimates based on the measurement of the lower first molar.

The variables we measured are Dirichlet nromal energy (DNE), three-dimensional orientation patch count rotated (3D-OPCR), and relief index (RFI).

Each page in this file represents one of our supplemental tables.

We have also included the MorphoSource DOIs for all specimens.

Table S1. List of specimens included in the estimate of body mass and results of the estimates based on the equations of Gingerich et al. (1982) and Conroy (1987).

Table S2. List of specimens included in the dental topographic analysis and results of the measurement of Dirichlet normal energy (DNE), three-dimensional orientation patch count rotated (3D-OPCR), and relief index (RFI) for the lower second molar.

Table S3. List of specimens included in the dental topographic analysis and results of the measurement of Dirichlet normal energy (DNE), three-dimensional orientation patch count rotated (3D-OPCR), and relief index (RFI) for the lower fourht premolar.

INSTITUTIONAL ABBREVIATIONS:

DMNH: Denver Museum of Nature and Science, Denver, Colorado; DPC: Duke University Fossil Primate Collection, Durham, North Carolina; USGS: United States Geological Survey, Denver (collections now at USNM); USNM: Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, D.C.; UW: Collection of Fossil Vertebrates, University of Wyoming, Laramie; YPM: Yale Peabody Museum, Yale University, New Haven, CT.