title: Sound localization in the alligator.
abstract: In early tetrapods, it is assumed that the tympana were acoustically coupled through the pharynx and therefore inherently directional, acting as pressure difference receivers. The later closure of the middle ear cavity in turtles, archosaurs, and mammals is a derived condition, and would have changed the ear by decoupling the tympana. Isolation of the middle ears would then have led to selection for structural and neural strategies to compute sound source localization in both archosaurs and mammalian ancestors. In the archosaurs (birds and crocodilians) the presence of air spaces in the skull provided connections between the ears that have been exploited to improve directional hearing, while neural circuits mediating sound localization are well developed. In this review, we will focus primarily on directional hearing in crocodilians, where vocalization and sound localization are thought to be ecologically important, and indicate important issues still awaiting resolution.
authors.affiliation: Center for Comparative and Evolutionary Biology of Hearing, Department of Biology, University of Maryland College Park, College Park, Maryland 20742, USA. Electronic address: hilaryb@umd.edu.
authors.forename: Hilary S
authors.initials: HS
authors.lastname: Bierman
authors.affiliation: Center for Comparative and Evolutionary Biology of Hearing, Department of Biology, University of Maryland College Park, College Park, Maryland 20742, USA. Electronic address: cecarr@umd.edu.
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Carr
mesh_terms: D000489:Alligators and Crocodiles / Q000033:anatomy & histology / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal; D005075:Biological Evolution; D055592:Biophysical Phenomena; D001717:Birds / Q000502:physiology; D003056:Cochlear Nerve / Q000033:anatomy & histology / Q000502:physiology; D004423:Ear / Q000033:anatomy & histology / Q000502:physiology; D016057:Evoked Potentials, Auditory, Brain Stem; D008322:Mammals / Q000502:physiology; D012104:Reptiles / Q000502:physiology; D013017:Sound Localization / Q000502:physiology*
keywords: Archosaur; Auditory periphery; Behaving alligator; Brainstem physiology; Pressure-difference receiver; Skull anatomy