I was watching an episode of Jurassic Fight Club on YouTube. (Strines may recognize it by its more-respectable name, Dinosaur Secrets.) The show is like an educational dino show crossed with Deadliest Warrior, down to the expert commentators with questionable credentials. But some are pros, so I watched.
Anyway, the linked episode is based on a fossil site found in Montana that included four Deinonychi that were apparently smashed perimortem and a Tenontosaurus with tooth marks that indicated it was partially eaten by one or more Deinonychuseses. Because of the proximity of the bodies someone drew the conclusion that a pack of more than four Deinonychus had attacked the Tenontosaurus. The herbivore fought back, killing four of its attackers with its tail or by rolling over on them. I’ll take their word for this interpretation, though I put little stock in anything said by a self-educated paleontologist who goes by the handle, “Dinosaur George.” If anybody is going to pretend he’s an expert her it’ll be me, by God!
While my eyebrow kept rising involuntarily throughout the show, what locked it in place was their description and animation showing how Deinonychus merely inhaled, with the used air running through their hollow bones and out through pores in their skin. I will admit that, prior to last night, I assumed birds and theropods had proper diaphragms, as God intended, but even the grossly-simplified animations of bird respiration showed them exhaling. So, my questions are:
Is there anything to that “exhaling through pores in their skin” thing?
How is that completely halfassed way that birds breathe “more efficient” than the way we, our parents, and our pet alligators have breathed for many millions of years, dammit?
Never heard of any such thing. Can you tell me what time the statement appears in the YouTube link, since I don’t want to watch the whole 14-minute video?
The air sacs make it a through-flow system, with no mixing of oxygenated air and and depleted air as in mammalian lungs. See the Wiki section on respiration under bird anatomy and this diagram. See also this video, and a more detailed explanation here.
Fourteen minutes? Dude, you need to wade through to 9:30 on Part 2! That’s Dinosaur George, by the way.
Where is there mixing in mammal lungs? Is it because we do not exhale efficiently? And does how our exhalation takes up half of a breath cycle mean we are really only taking breaths half as often as a bird?
I hate all the animations that show only one full cycle instead of multiple cycles, where the greater efficiency will be more obvious. Some people are more visual, and I may need to draw it myself, in CAD or in my brain. That was how I figured out why Harleys have that nasty rough idle. (Two cylinders 45 deg apart, both pistons on the same crankpin? Bad design 100 years ago.)
It doesn’t say the air exited through “pores in their skin,” it says it “exits the body through holes in some of the bones.” I think that he’s just garbled what he is saying somewhat. Air passes from the air sacs into some of the hollow bones (in both birds and theropods), then passes back into air sacs before ultimately exiting through the trachea.
In the entire lung.
We don’t expel all the air contained in the lung with each breath, so there is always some “stale air” inside our lungs that’s depleted of oxygen. Birds lungs are always filled with air that has the same oxygen content as the outside.
Not sure what you mean. Birds require two inhalation-exhalation cycles to pass a lungful of air completely through the respiratory system.
The animation garbles it, too, showing the stale air wafting out of its back instead of its mouth. But it’s the History Channel, so what can one expect?
I have to give this more thought. Maybe more research, too, but that’s cheating.
BTW, although I’m sure it is mentioned (or rather, not mentioned) in Colibri’s links, birds and all other vertebrates lack a diaphragm. That is a mammalian feature. And it is a good thing (in our system) that we always have some stale air between each breath. Bad things happen when the percentage of residual air to exhaled air changes (either too much residual or too little residual air).
The Deinonychus in particular are some of the worst dinosaur models I’ve ever seen in the modern era. They look like they were based directly on the very first reconstructions of the animal from the 1970s, before its anatomy or relationships were well understood.
Consensus opinion among paleontologists right now seems to be that the evidence for pack hunting from the Tenontosaurus site is not so easily interpreted and may in fact represent uncoordinated or semi-coordinated, “selfish” mobbing behavior as seen in many birds and lizards. Much is made of the fact that many of the Tenontosaurus bones have Deinonychus bite marks. Little is made of the fact that some of the Deinonychus bones also have Deinonychus bite marks. Looks like a feeding frenzy, not a wolf pack. http://www.bioone.org/doi/abs/10.3374/0079-032X(2007)48[103%3AAROCPH]2.0.CO%3B2
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