Fossils of Jeholbaatar kielanae (pictured in a drawing above) was discovered by researchers in China and may help reveal how and why mammals


New ancient species of rodent discovered in a fossil from China is found to have a unique inner ear structure not seen in any other mammal

  • Researchers discovered a new species of rodent-like mammal in fossils 
  • Among the defining features are a strange inner ear arrangement 
  • Researchers say the mammals ears were influenced by dietary preference
  • The findings may help shed light on evolutionary history of mammals bones

A new species of rodent-like mammal discovered by researchers in China is shedding light on an unheard of form of hearing.

Well preserved fossils of the creature, dubbed Jeholbaatar kielanae, were discovered in the Jiufotang Formation in China’s Liaoning Province, and studied by the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing.

Scientists say the ancient mammal, which comes from a species called multituberculates, weighed about  1.5 ounces and lived about 120 million years ago, meaning it co-existed with dinosaurs during the Cretaceous period.

Fossils of Jeholbaatar kielanae (pictured in a drawing above) was discovered by researchers in China and may help reveal how and why mammals’ hearing evolved over time

Among its defining features, according to a report published today in the journal Nature, is a strange hearing apparatus that may give insight into how and why mammals sense of hearing evolved over time.

Well-preserved fossils show a strange alignment of bones in the creatures’ ears with the a small bone called the incus located behind a larger bone called the malleus.

Scientist say the alignment is significant because, while also conducive to hearing some varieties of sound, it helped achieve a type of chewing motion fueled by a preference for certain types of food.  

Instead using a vertical biting motion like a cat or moving their lower jaw sideways like a cow they sliced and ground food by drawing it backwards.

This enabled them to use plants as a food source at a time in pre-history when other mammals mainly ate insects or small vertebrates.

‘The specimen provides important evidence regarding mammalian middle-ear evolution… Jeholbaatar would suggest the development of the middle ear in multituberculates was triggered by requirements for feeding,’ Corresponding author Yuanqing Wang, of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, said

‘Based on the shape of the lower cheek, Jeholbaatar would have had an omnivorous diet – feeding on worms, arthropods and plants. It had a distinct jaw movement while chewing.’

The key finding, researchers say, is that feeding appears to have an influence on the mammalian jaw and ears – a connection that may help give insight to how and why animals changed their hearing apparatuses throughout the evolutionary chain.

HOW DOES BONE CONDUCTING WORK?

In bone conduction listening, the bone conduction devices (such as headphones) perform the role of your eardrums. 

These devices decode sound waves and convert them into vibrations that can be received directly by the Cochlea so the eardrum is never involved.

The ‘sound’ reach the ears as vibrations through the bones, or skull, and skin. 

How it works: 

Most sounds are heard by our eardrums. The eardrum converts the sound waves to vibrations and transmits them to the cochlea (or inner ear). 

However in some cases vibrations are heard directly by the inner ear bypassing your eardrums. 

In fact, this is one of the ways you hear your own voice. This is also how whales hear.

Ludwig van Beethoven, the famous 18th century composer who was almost completely deaf, discovered Bone Conduction. 

Beethoven found a way to hear the sound of the piano through his jawbone by attaching a rod to his piano and clenching it in his teeth. 

He received perception of the sound when vibrations transfer from the piano to his jaw. 

This has proven that sound could reach our auditory system through another medium besides eardrums and the other medium is our bones.

Since bone conduction does not use the eardrums, people with hearing difficulties would be able to hear clearly again with bone conduction, provided that their cochlea is in healthy and normal condition. 



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