DISSERTATION RESEARCH: Evolution of the Cranial Cavity in Mammals and Extinct Cynodonts

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Abstract for DEB-0309369A grant has been awarded to Dr. Timothy Rowe and Mr. Ted Macrini of The University of Texas at Austin to study the evolution of the braincase, endocranial cavity, and brain in Recent mammals and some of their closest extinct relatives within Cynodontia. The relative importance of different sensory modalities, endocranial capacity, and intelligence will be assessed for selected Recent and extinct specimens, chosen to represent the last 200 million years of mammalian diversification. X-ray computed tomographic (CT) scanning will be used to quantitatively explore different components of sensory acuity, behavior, and intelligence through the examination of digital endocasts, or three-dimensional infillings of the braincase. Brains rarely, if ever, fossilize, but brain volume and external shape are often preserved by the bones of the braincase that enclose the endocranial cavity. Until recently natural endocasts were largely unobtainable without destroying the specimen. X-ray CT permits non-destructive recovery of endocranial surfaces and volumes from living and extinct species never before studied in this capacity. Comparisons will be made between endocasts and actual brains in Recent species, and between those extinct species whose phylogenetic positions are relatively well constrained. Scanning will be performed by the University of Texas High-Resolution CT Facility, an NSF-sponsored Multi User Facility.This study will generate large volumes of high quality digital data and visualizations of interest to the wide audience that studies the evolution of mammalian behavior and intelligence. Data generated in this study may also help resolve persistent problems in mammalian systematics. Legacy data generated by this study will be distributed via www.DigiMorph.org, an NSF-sponsored Digital Library of Vertebrate Morphology.