Understanding the evolution of the earliest primates

点击翻译按钮获取中文摘要

The first members of our own Order, the Primates, appear shortly after the extinction of the non-avian dinosaurs, some 65 million years ago. In the early years of the Age of Mammals these primitive primates flourished, producing an impressive diversity of different forms. The current project seeks to better understand the processes by which primates originated and diversified from three different perspectives. First, fieldwork in Wyoming and Montana will seek to uncover new specimens of poorly known groups of early primates. Excavations in approximately 54 million year old deposits in the Bighorn Basin of Wyoming will seek new material of the rare Picromomyidae, a family known from only 11 specimens. This family includes one of the smallest primates ever documented (Picromomys petersonorum), which only weighed around 10g, making it a third the size of the smallest living primate. Work at Dorsey Creek Quarry, the site that has produced the best material for this elusive family, will seek to add to our knowledge of this tiny primate. Research in older deposits (~62 mya) in the Crazy Mountains Basin of Montana will also expand what we know about one of the most primitive families of primates, the Palaechthonidae. As one of the first primate groups to diversify, expanding our knowledge of this family is central to understanding the later rich diversity of our Order. Work in both locations will focus on periods of significant climate change, shedding light on how such changes can affect the mammalian fauna, which is relevant to modeling the effects of future climate change. Second, the largest single sample of stem primates, including more than 1500 specimens of known age, will be studied to document patterns of evolution in one family, the Microsyopidae. This large sample provides a unique opportunity to not only document evolutionary change as it happened, but to potentially explain the causes of that change. Cutting edge dental topographic methods for quantifying aspects of the tooth shape will make it possible to consider how periods of climate change related to shifting diets in this group. Finally, high resolution X-ray computed tomography (CT) data will be used to reconstruct endocasts (internal models of the skull which reflect brain anatomy) from fossil primates and from our close living and fossil relatives, including rodents and rabbits. This research will provide a better understanding of what is primitive for Primates in terms of the size and form of the brain, and better characterize the very earliest stages in the development of the exceptionally large human brain. In sum, this project aims to provide a better understanding of the early phases of primate evolution, helping to characterize the evolutionary backdrop against which humans ultimately evolved.