Originally published at: https://boingboing.net/2024/07/05/how-an-angel-sharks-appearance-changes-when-it-yawns.html
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Sheesh. No wonder this fish is alone.
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From Popkin!
For the BBS
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Cool!
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I find it oddly endearing that even sharks yawn. Also, considering how ancient they are, how far back in the evolutionary chain does yawning go?
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TBF most people look a little undignified mid-yawn.
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Good question, sharks existed before trees did, so it definitely goes back a long ways…
Now I’m wondering “do insects have an equivalent of a yawn?” and the answer is no, it seems relegated to species with lungs. 
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I thought sharks had gills?
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Dragonfly and damselfly nymphs have even more Alien-like jaws:
Dragon:
Damsel:
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I think our common ancestor with sharks and rays would have to mark the start. The next step back are the jawless fish, some surviving in the form of lampreys and hagfish, and they…don’t have jaws for it.
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I luv them, eating mosquitoes from birth to death…
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Excellent point, I guess the blood/oxygen gas exchange system must be more advanced than the insect spiracle respiration.
As I’m thinking about this, I guess I always thought of gills as “lungs on the side of the throat” rather than mammalian internal lungs.
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When I think of lungs on the side of the throat, I think of newts.
In my head the main difference between lungs and gills is where and from what they’re most efficient at obtaining oxygen, but I’m an old hand at being wrong.
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That’s how the terms are used as a rule, gills for taking oxygen from water and lungs as chambers for taking it from the air. People do make exceptions when a structure for one is being used for the other, like how some crustaceans use gills on land but they’re still flat sheets that need to stay wet. The two can be related though, like the book lungs of spiders and the gills of horseshoe crabs. (Of course you wouldn’t really yawn for those, or the spiracles of insects, simply because they are not related to the mouth.)
Vertebrates have gills and lungs that develop in very different ways. Gills are supported by pharyngeal arches that could also be used in feeding, and in fact our mandible comes from those too. Jawless fish and sharks don’t have any equivalent of our lungs. They first showed up in early bony fish, and still exist along with gills in lungfish and bichirs. Modern coelacanths have vestigial lungs filled with fat for buoyancy, and in other fish they became the swim bladder, which is in the middle of the body so is better for balance.
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Is this a Biblically-accurate Angel shark?
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