Fossil skeletons of the first primates are extraordinarily rare, limiting our understanding of their ecology, anatomy, and evolution. Despite their rarity and central importance to understanding the initial steps in the biological radiation that ultimately includes humans, the most completely known skeletons from North America remain uncollected and unstudied, with museum specimens largely still entombed in rock and in need of preparation. To address this problem, the research team will 'virtually' extract the most complete primate skeletons yet known from the Eocene (48 million years old) of North America using 3D imaging technology for museum samples and newly collected specimens from the Bridger Basin, Wyoming. These three-dimensional images provide uniquely informative quantitative morphometric data that will be analyzed in the context of a massive comparative 3D digital dataset of fossil and extant primate specimens, utilizing sophisticated statistical and mathematical techniques.
While it is generally accepted that these early primates were most similar to the lemurs of Madagascar among living primates, preliminary analyses have begun to suggest that this perspective is not entirely accurate. Because of their completeness, Bridger skeletons provide evidence allowing critical tests of these ideas, transforming understanding of early primate evolution through detailed analyses of their anatomy in evolutionary context. Additionally, new evidence on the anatomy of early primates will allow tests of competing phylogenetic hypotheses about whether these Eocene primates are more closely related to anthropoids (monkeys, apes, and humans), strepsirrhines (lemurs, lorises, and galagos), or perhaps represent a more primitive branch of the primate tree. Finally, Bridger skeletons will provide the first detailed characterization of locomotor and positional behavior in these specimens, clarifying this aspect of the adaptive context for the origin and early evolution of primates. Examining the anatomy of the new skeletons in evolutionary context will test the idea that several early primate lineages may have independently evolved specialized acrobatic leaping, previously considered to be a uniting characteristic of primates.
This project includes the involvement of five undergraduate students; a postdoctoral scholar; hosting of lab and field workshops involving K-12 educators, fossil clubs, and local museums; and posting of digital atlases of skeletons on a publicly accessible website (www.morphosource.org). MorphoSource allows both researchers and the public to study every detail of each skeleton (including in situ bone positions) processed by the investigators. A digital atlas of 3D data and other related images will be published, providing both improved archival documentation and enhancing participation by all interested individuals in the discovery process. In this aspect, the project can be seen as a model for future research in its transparency through exhaustive, open-access documentation of research materials.
