Evolution, Development, and Ecology of Biomineralized Tissues

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The evolution of bones and teeth is an adaptive breakthrough that led to the radiation of vertebrate animals. Not only do they provide support, energy, and increase functional capability, bones and teeth also capture a record of an animal's life history through the formation of growth marks and changes in chemical composition during biomineralization. This record is used to infer life history traits such as growth rates, time of reproduction, and survivorship, and ecological traits such as dietary preference and trophic levels in food webs. Fortuitously, this record can also be captured in fossilized remains, thereby allowing for an interpretation of life history traits and ecology in extinct animals based on patterns in living animals. However, the microanatomical structure of these growth marks and their formation and variation in living animals is not fully understood, especially how environmental factors like seasonality and limited resources impact biomineralization. The long-term objective of this research program is to integrate data from the fields of paleontology, evolutionary developmental biology (Evo-Devo), ecology, and geology to interpret the life history and ecological niche of extinct vertebrates through examination of bone and tooth ultrastructure. This research program will train 12 HQP over the next five years in both lab and field work. Different types of imaging and microscopy will be used, including computed tomography and optical microscopy, with a relatively new approach to studying vertebrate fossils at the nanoscale using transmission electron microscopy. Detailed characterization of growth marks in biomineralized tissues from the macro- to the nanoscale in living reptiles (leopard geckos and green anoles) will elucidate how these structures form, the rate at which they form, and under what conditions. Only then, armed with the information gathered from living animals, can meaningful interpretations of extinct animal ecology from fossilized growth marks be undertaken. Furthermore, analyzing the chemical composition of the biomineralized tissue in living animals is paramount to separating biological chemical signatures from diagenetic signatures in fossil material. Data collected from individuals can then be examined in a comparative context over long, million-year timescales to determine relationships between vertebrate life history and environmental change in deep time.