The human middle ear plays a key role in transporting sound into the inner ear and allowing us to hear.
Fossil evidence shows that the human middle ear is from a fish. The origin of the spiracle has been a mystery for many years.
Researchers in the 20th century searched for a spiracular gill between the mandibular and hyoid arches. There were no fossils found in any of the research done over the past century.
Scientists from the Chinese Academy of Sciences and their partners have found clues to the mystery of armored galeaspid fossils.
The findings were published in a journal.
The first 419-million-year-old galeaspid fossil and the first 437-million-year-old Shuyu 3D braincase fossil have been found by researchers over the last 20 years. The fossils were found in three different provinces.
The first evidence of a fish spiracle came from these fossils.
The virtual endocasts of the Shuyu brain case were reconstructed. The skull of Shuyu contains a number of brain divisions, sensory organs, and cranial nerve and blood vessel passages.
Our teeth, jaws, middle ears, and many other structures can be traced back to our fish ancestors. According to the academician of the Chinese Academy of Sciences, Shuyu is one of the missing links.
The spiracle is a small opening in the eye of a fish. The intake of water into the buccal space is done by the spiracle. The spiracle can be found near the top of the animal allowing it to breathe.
The spiracles are used to breathe in air in the Polypterus. As non-fish species evolved to breathe through their noses and mouths, fishspiracles were replaced. The spiracle appears to have developed first into the Otic notch. It wasn't able to sense sound like the spiracle. The hearing canal used to transmit sound to the brain was created by the spiracle. This function has been with us for a long time.
The entire history of the spiracular slit has been bridged by our finding, which brings together recent discoveries from the gill pouches of fossil jawless vertebrates, via the spiracles of the earliest jawed vertebrates.
More information: Zhikun Gai et al, The Evolution of the Spiracular Region From Jawless Fishes to Tetrapods, Frontiers in Ecology and Evolution (2022). DOI: 10.3389/fevo.2022.887172 Journal information: Frontiers in Ecology and Evolution
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