Traditionally, the ear region is the preeminent source of comparative morphological information for evolutionary studies on mammals. It also presents one of the most oft cited examples of evolutionary change in Biology textbooks: the evolution of the three middle-ear bones (ossicles) of mammals from the lower jaws of more primitive forms. Despite its preeminence, knowledge of the ear region remains incomplete. During recent years, remarkable fossil finds have dramatically increased what is known of the ear and its ossicles in extinct mammals and raised questions about previous views on the evolution of this region and of mammals in general. To fully evaluate these fossils and new evolutionary questions, it is necessary to increase comparative knowledge of the ear in modern mammals, both in numbers and in level of detail. This research gathers comparative information on the embryology of the ear region in modern mammals to evaluate the evolution of this complex system and its role in the evolutionary history of mammals.
