R touches half a jaw of a deinosuchus, precursor to alligators. This fossil (or rather, a cast of an actual fossil) was provided by the University of Texas at Austin Jackson School of Geosciences, Museum of Earth History. A bright yellow jawbone behind it is a skull of a modern day caiman, for comparison. It has the same shape, only it is several times smaller. The deinosuchus was as big as a school bus.
This was one of the exhibits at the Darwin Day, hosted by the Center For Inquiry Austin at the University of Texas J. J. Pickle Research Center.