Earliest known bird had hearing similar to an emu

15 January 2009

The earliest known bird, magpie-sized Archaeopteryx lithographica, could hear just the same as a modern emu (Dromaius novaehollandiae), demonstrating that Archaeopteryx was bird-like rather than reptilian, according to new research published this week.

Using innovative modern technology, palaeontologists at the Natural History Museum in London have shown for the first time how the length of the inner ear of birds and reptiles can be used to accurately predict their hearing ability.

Illustration of the Archaeopteryx

Illustration of the Archaeopteryx by John Doncaster. Copyright NHM.

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

Previously, researchers have only been able to estimate how prehistoric animals heard sounds by examining the skulls of damaged fossils and relating brain region size to hearing ability, based on comparison with the fossil's modern counterpart. However, modern computed tomography or CT imaging allowed Dr Barrett and his colleagues to accurately reconstruct the inner ear anatomy of various intact bird and reptile specimens.

"Hearing ability in living species is relatively easy to measure, but such direct evidence cannot be gained from extinct animals for obvious reasons - we can't just play sounds to a dinosaur and see how it responds to the noise. This has meant that we have not been able to fully understand how different animals developed hearing during their early evolution, until now that is," continued Dr Barrett.

Dr Stig Walsh explained, "By examining the three dimensional CT scans, we were able to see for the first time the real relationship between hearing ability and behaviour in extinct reptiles and birds. The size of the cochlea duct (the bony part of the inner ear, housing the hearing organ) in living birds and reptiles accurately predicts the hearing ranges of these animals. This simple measurement can therefore provide a direct means for determining hearing capabilities and possibly behaviour in their extinct relatives, including Archaeopteryx."

Dr Angela Milner explained, "This adds yet more information about how bird-like Archaeopteryx was. Our previous research has shown that the part of the ear that controls balance was just like that of modern birds. Now we know that Archaeopteryx had bird-like hearing, too."

Animals with a long cochlear duct tended to have the best hearing and vocal ability. Modern living bird species are known to possess relatively longer cochlear ducts than living reptiles. A long cochlear duct is also an indicator of an individual's complex vocal communication, living in groups and even habitat choice. This is true for both mammals and birds.

"Species living in large social groups have more complicated vocal communication which is understandably influenced by an individual's ability to hear. Species living in a closed environment, such as forests, where visual communication is ineffective often posses more complex vocal abilities, so now we can more accurately predict the habitat types that extinct animals lived in by examining their ability to hear and communicate," concluded Dr Barrett.

The research received funding from the Natural Environment Research Council (NERC) and the findings are published in the latest issue of the Proceedings of the Royal Society B.

Further information

For further information, images or to arrange an interview please contact:

Claire Gilby
Senior Press Officer
Natural History Museum
Tel: 020 7942 5106

NERC Press Office
Natural Environment Research Council
Polaris House, North Star Avenue
Swindon, SN2 1EU
Tel: 01793 411561
Mob: 07917 557215

Notes

1. 'Inner ear anatomy is a proxy for deducing auditory capability and behaviour in reptiles and birds' is published in Proceedings of the Royal Society B.

2. Dr Paul Barrett, Dr Stig Walsh and Dr Angela Milner, all from the Natural History Museum, worked with colleagues Dr Lawrence Witmer at Ohio University and Dr Geoffrey Manley at Munich University.

3. 59 species from 52 genera representing Testudines (turtles, tortoises and terrapins), Crocodylia (crocodiles, caimans and alligators), Rhynchocephalia (beak-headed reptiles), Squamata (snakes and lizards) and eight avian orders formed the basis for this research.

4. Dr Barrett et al studied the endosseous cochlear duct (ECD) to assess the hearing capability of early birds and reptiles.

5. Archaeopteryx lithographica is the earliest-known flying bird, about the size of a magpie. It is one of the most valuable scientific specimens in the Museum's collection. The finest specimen of Archaeopteryx lithographica was found in 1861 in a quarry in Solnhofen in Bavaria, southern Germany. A lithographic limestone slab was split in two, exposing a fossil that had teeth and claws like a reptile and feathers like a bird. In the same year, the geologist Herman von Meyer of Frankfurt announced its discovery to a stunned and amazed world. The specimen is now part of the palaeontology collections at the Natural History Museum, London. Dr Angela Milner led research that revealed the anatomy of the ears in Archaeopteryx, which was published in Nature in 2004.

Press release: 01/09

Earliest known bird had hearing similar to an emu

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