Click here to visit my Web site on paleontological research in the Rio Gallegos area of Argentina.
Evolution of Primates and of Mammalian Faunas in South America
For the past 35 years, I have been engaged in research in Colombia, Ecuador, Argentina, Bolivia and the Dominican Republic with three objectives:
1. to reconstruct the evolutionary history and adaptive patterns of South American primates and other mammals;
2. to establish a more precise geologic chronology for the mammalian faunas between the Late Eocene and Middle Miocene (between about 36 and about 11 million years ago); and
3. to use anatomy and niche structure of modern mammals as a means to reconstruct the evolution of mammalian niche structure in the Neotropics.
Primate Anatomy -- Implications for Phylogeny and Adaptations
A major theme of my work is to improve our understanding of two related topics:
1. the phylogeny of primates based (principally) on anatomical evidence; and
2. inferring the adaptations of extinct primates based mainly on cranial and dental evidence.
Plans for Future Research
Plans for research over the next 3-5 years are embodied in three projects.
1) Climate Change in the mid-Miocene of South America
One is a particularly important region of Patagonian Argentina encompassing a rock unit called the Santa Cruz Formation that spans the mid-Miocene Climate Optimum, a period of particularly significant climatic warming when the earth’s subtropical zone stretched to the southern end of the South American continent. This project concentrates on the reconstruction of the mammalian niche structure using modern mammalian assemblages of known species richness and ecology. The paleoecology of extinct mammalian species is inferred using ‘ecomorphology’-- using anatomical features to reconstruct the niche of extinct species.
2) Paleontological Investigations to Recover Fossil Monkeys from the Middle Cenozoic of South America
The pattern of monkey evolution in South America is poorly documented and little understood. Some argue that New World monkeys (Platyrrhini) known from 16-20 million year old rocks of Patagonia predate the origins of the modern families, that is, they are 'stem platyrrhines'. Others argue that they are early representatives of the modern platyrrhine families. The two alternative interpretations have profound implications for how the evolutionary radiation of platyrrhines is viewed. Further fossil material of early platyrrhines will contribute to resolving this debate. A joint team of US and Argentine paleontologists are searching for fossil primates in Patagonian Argentina. Collecting will concentrate on proven localities and expand collecting efforts to other lesser-known sites said to be richly fossiliferous from the Atlantic coast inland to the Andean front at 50-55 degrees South latitude.
3) The Dynamics of Mountains, Landscapes and Climate in the Distribution and Generation of Biodiversity of the Amazon/Andean Forest
The forests of tropical South America host some of the highest biodiversity on Earth. I am collaborating with, an interdisciplinary team of geologists, climatologists, and biologists will take advantage of recent advances in their respective disciplines to develop an integrated understanding of how climate and geology interact to shape the distribution and generation of biodiversity in these Amazon/Andean forests through time. The Amazon and Andes are a dynamically linked highly interactive system. On long timescales, uplift of the Andes affects Amazon climate and hydrology. Andean uplift also generates the sediment fill, nutrient supply, river routing, and soil composition of the adjacent lowland basin of the Amazon and hence affects the productivity of its forests. But the interactions are bi-directional, because changes in climate, hydrology, and sediment supply influence rates of uplift through isostatic (buoyancy) effects produced by weathering and erosion. Together the multiple system components interact in complex ways to effect the origin and demise of new species and thus determine biodiversity. Today, this biodiversity is threatened by global climate change and other human activities. For example, a major emerging threat is the planned construction of headwater dams that will sever the transfer of nutrients from the Andes to the Amazon and impact the productivity and diversity of its forests and waterways. Thus, more than ever, there is a need for better understanding of the factors that foster the evolution and maintenance of biodiversity. The project is an interdisciplinary effort that unites scientists from both North and South America. It will support the education, training, and mentoring of undergraduate students, graduate students, and postdoctoral scientists at this exciting new frontier through the integration of fieldwork, laboratory studies, and modeling.
Before it is possible to quantify relationships between extrinsic forcings (e.g. climate, tectonics, hydrology) and the observed distribution of species through time, it is first necessary to generate accurately dated histories of the underlying geologic and climatic processes and to explore the governing rules for how environment influences diversity. I am collaborating on the construction of an over-arching modeling framework linking paleo-topography, climate, hydrology, on one hand, to mammalian ecologic niche, and species distribution, on the other hand.
Coastal exposures of the Santa Cruz Formation in southern Patagonia have been a fertile ground for recovery of Early Miocene vertebrates for more than 100 years: studies began in the 1840s when specimens were sent for study to Charles Darwin. The formation is noted for yielding remarkably complete specimens, and a richly varied taxonomic assemblage very different from other continents, due to the long isolation of South America. This volume presents the most comprehensive compilation of important mammalian groups which continue to thrive today. It includes the most recent fossil finds as well as important new interpretations based on 10 years of fieldwork by the authors. A key focus is place on the paleoclimate and paleoenvironment during the time of deposition in the Middle Miocene Climatic Optimum (MMCO) between 20 and 15 million years ago - a transient warming event similar to our current climate. Using newly recovered pollen, phytoliths and plant macrofossils together with invertebrates, amphibians and reptiles, the authors present the first reconstruction of what climactic conditions were like for this most southerly continental record of the MMCO. They also present important new evidence of the geochronological age, habits and community structures of fossil bird and mammal species. Academic researchers and graduate students in paleontology, paleobiology, paleoecology, stratigraphy, climatology and geochronology will all find this a valuable resource of information about this fascinating geological formation.