Evidence from the fossil record reveals that the ear region of the skull changed radically during the evolutionary transition from reptiles to mammals. Many of these changes concerned soft- tissue structures (nerves, arteries, and veins), as evidenced by various grooves, canals, and foramina in the fossils. Our ability to interpret these bony features in fossil forms is severely limited by poor knowledge of soft-tissue structures in the ear region of modern mammals. Detailed anatomical data from modern mammals will be collected and used to: (1) reconstruct soft-tissue structures in the ear regions of fossil forms and (2) analyze the evolutionary relationships among the major groups of mammals.
