Lend me your ears. Using inner ear structure to deduce hearing capability and behavior. The inner ear is a pretty useful little organ in that it provides our sense of balance or equilibrium and helps coordinate eye movements, but, of course, ears also are for hearing. The cochlea is the hearing portion of the inner ear, and so information about its size or shape can shed light on hearing capabilities, as well as other behaviors. The inner ear is buried deep within t he skull, and so CT scanning was used to peer inside the skulls of 59 species of modern reptiles and birds. From these CT data, the inner ears were visualized in 3D, and various measurements of the cochlea were made. These measurements were then compared to a variety of hearing parameters and other biological attributes of the modern species. It turned out that the dimensions of the cochlea indeed relate to hearing frequency range and what frequencies are heard best, but, more surprisingly, also relate to complexity of vocalizations, sociality or living in large groups, and maybe even, in very general terms, preferred habitats. Armed with this information gleaned from the modern realm, attention was turned to some fossil birds and, in particular, Archaeopteryx, the oldest known bird. The 145-million-year-old fossils of Archaeopteryx have been known since Darwin’s time, when it quickly was heralded as an important “missing link,” because it combined birdlike feathers and wishbone with the teeth and long tail of a small dinosaur. CT scans of Archaeopteryx reveal that its cochlea is much more similar to that of modern birds, and that its hearing capabilities were much like those of modern emus (which is not particularly a compliment). This study opens the door for future research into other extinct animals, such as the dinosaurian relatives of birds, providing the prospects for even more refined estimates of dinosaur behavior and ecology

Image caption: The cochlea of the inner ear of the 145-million-year-old bird Archaeopteryx can be reconstructed from CT scans of fossils. Based on comparisons with modern reptiles and birds (such as the emu at lower left), new insights into such behaviors as vocal complexity and sociality can now be better understood in extinct taxa. Courtesy of Witmer & Ridgely, Ohio Univ., and NHM, London.