January 14, 2009

Prehistoric Reptile Had Hearing Like Modern Birds

New British research finds that the Archaeopteryx lithographica seems to have been more like a bird than a reptile in terms of hearing ability.

The researchers based their conclusion on their discovery that the length of a part of the inner ear of reptiles and birds can help predict their hearing ability.

The team examined whether the length of the cochlear duct, which lies in the inner ear and is part of the cochlea, could be used to deduce hearing ability in a group of modern birds and reptiles such as the emu, barn owl, alligator and green turtle.  Such modern bird species are known to have longer cochlear ducts than living reptiles.

Indeed, the study's results confirmed that animals with a long cochlear duct were more likely to have better hearing and vocal ability.  And for both mammals and birds, a long cochlear duct is also an indicator of vocal communication, living in groups and even habitat choice.

"In modern living reptiles and birds, we found that the length of the bony canal containing the sensory tissue of the inner ear is strongly related to their hearing ability," paleontologist Dr Paul Barrett, a with the Natural History Museum told BBC News.

"We were then able to use these results to predict how extinct birds and reptiles may have heard, and found that Archaeopteryx had an average hearing range of approximately 2,000 Hz," he said.

"This means it had similar hearing to modern emus, which have some of the most limited hearing ranges of modern birds."

Previous research had only been able to make an educated guess about how well prehistoric animals heard sound.  They accomplished this by examining skulls of damaged fossils and correlating the size of areas of the brain used in hearing to actual hearing ability. Researchers used comparisons with the fossil's living counterpart to make a final estimate of hearing ability.

However, with the use of modern computed tomography (CT) imaging, Dr Barrett and his team were able to accurately reconstruct the inner ear anatomy of a variety of intact bird and reptile specimens.

The study was published in a journal of the UK Royal Society.


Image Caption: A model of Archaeopteryx lithographica on display at the Oxford University Museum. Courtesy Wikipedia


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