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Tetrapod Spiracles; tetrapods with spiracles and alternative forms of hearing.
Topic Started: Oct 1 2010, 12:53 AM (493 Views)
Toad of Spades
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Clorothod
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Tiktaalik and its close relatives were known to have used their spiracles to breath air, and as with other fish, their sac-like nostrils were not connecting with the oral cavity. In tetrapods the spiracles sealed off to become the eustachian tubes and the nostrils connected with the mouth to be involved in breathing.

So what if tetrapods evolved to keep use their spiracles in breathing instead of using their nostrils? Their spiracles would be like nostrils on the top of the head and the actual openings could be positioned for different lifestyles.

This brings up another question as well. If tetrapod breathing evolved this way, what would be used for hearing? In fish part of the inner ear opens directly into the water, with no tympanium. With no eustachian tubes or eardrums, what kind of structures would develop around the inner ear to allow for hearing out of water?


What are your thoughts and opinions?



Also here are some things I wonder about and would like to hear your opinions.


-Why didn't they evolve this way instead of how our timeline's did?

-Why did nostrils become involved in breathing?

-Why did Tiktaalik and its relatives evolve spiracles instead of just breathing directly through their mouth?
Edited by Toad of Spades, Oct 1 2010, 01:49 AM.
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colddigger
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I personally think that nostrils became involved in breathing because they were used for smelling, and drawing in air through the act of breathing drew in more air through the nostrils and gave the nose breathers an advantage in that ... fashion. But I'm sure there's a real reason out there that has evidence supporting it, or something.
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