RESEARCH

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I study patterns of biotic change in terrestrial ecosystems using microvertebrate assemblages, which are fossilized deposits of bones from  small-bodied vertebrates which accumulate in river and lake settings. These assemblages are one of the best proxies for vertebrate biodiversity and food web interactions in the sedimentary rock record. I sample assemblages at stratigraphic intervals to build high resolution records of biotic change over geologic timeframes. Patterns of change are then correlated to concurrent Earth system events to study the effects of bolide impacts, volcanism, plate tectonic movement, and climate change on terrestrial ecosystems. 

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Late Triassic Biotic Change in North America

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My main study system is the Chinle Formation in southwest North America,

which was deposited by rivers and lakes over the last 25 million years of the

Late Triassic. I am sampling microvertebrate assemblages at <1 million year

intervals through the Chinle Formation to quantify patterns of diversity and

trophic change over the Late Triassic. Radioisotopic dates bracket these

assemblages, and allow for the precise correlation of patterns of biotic

change to causal factors including the Manicougan Bolide impact (~215 mya)

and the collapse of the Late Triassic Megamonsoon. I am also studying patterns

of biotic change using microvertebrate assemblages from the Late Triassic aged

Newark Supergroup in eastern North America. I plan on time-calibrating patterns

of ecological change from the Chinle Formation and Newark Supergroup to

understand whether observed trends are regional or global, especially with

regards to the ecological effect of the Manicougan Bolide impact. 

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Lepidosaur Evolution in the Early Mesozoic

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Lepidosaurs, the reptile group including lizards, snakes, and the tuatara, undergo a rapid and global diversification during the Triassic. Through studying microvertebrate assemblages in the Chinle Formation I have discovered many new species of early lepidosaurs which occupied a range of ecological niches in the Chinle vertebrate ecosystem. I use the stratigraphic occurrence and evolutionary relationships of these lepidosaurs to analyze the timing of their evolution, showing that the end-Permian extinction was the likely driver of lepidosaur diversification in the Triassic.  I am interested in studying the evolution of lepidosaurs in relation to other Earth system events such as the Manicougan Bolide impact and the end-Triassic extinction.