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RE: Unidirectional gator breathing in Science
One question this raises... is the crocodilian unidirectional lung basal for
archosaurs, or does it represent a "tuned down" remnant of an even more
avian-like respiratory system which may have existed in early crocodilians if
they were endotherms? Crocodilians exhibit other features suggestive (four
chambered heart, separation of respiration from locomotion) of more
metabolically active ancestors.
> Date: Thu, 14 Jan 2010 23:30:15 +0100
> From: Heinrich.Mallison@mfn-berlin.de
> To: firstname.lastname@example.org
> Subject: Re: Unidirectional gator breathing in Science
> Wow, just wow! I LOVE it when a plan comes toge.... ah, no, wrong movie.
> Seriously, I love this: Steve Perry a long time ago (IIRC in Biology of the
> Reptilia) pointed out that the tissue organisation in croc lungs was very
> close to birds, and now we see it is even closer than he thought!
> Add a bit of intersting dino lung trivia: air exchange volume for
> Plateosaurus is ~20l, per body weight a typical bird value.
> Dr. Heinrich Mallison
> Museum für Naturkunde Berlin
> Invalidenstrasse 43
> 10115 Berlin
> -----Ursprüngliche Nachricht-----
> Von: owner-DINOSAUR@usc.edu im Auftrag von Andrew Farke
> Gesendet: Do 14.01.2010 22:55
> An: email@example.com
> Betreff: Unidirectional gator breathing in Science
> Saw this presented at SICB a few years ago - super cool stuff!
> Farmer, C.G., and K. Sanders. 2010. Unidirectional airflow in the
> lungs of alligators. Science 327(5963):338-340.
> DOI: 10.1126/science.1180219
> The lungs of birds move air in only one direction during both
> inspiration and expiration through most of the tubular gas-exchanging
> bronchi (parabronchi), whereas in the lungs of mammals and presumably
> other vertebrates, air moves tidally into and out of terminal
> gas-exchange structures, which are cul-de-sacs. Unidirectional flow
> purportedly depends on bellowslike ventilation by air sacs and may
> have evolved to meet the high aerobic demands of sustained flight.
> Here, we show that air flows unidirectionally through parabronchi in
> the lungs of the American alligator, an amphibious ectotherm without
> air sacs, which suggests that this pattern dates back to the basal
> archosaurs of the Triassic and may have been present in their
> nondinosaur descendants (phytosaurs, aetosaurs, rauisuchians,
> crocodylomorphs, and pterosaurs) as well as in dinosaurs.