"Modern birds sustain their flight with an efficient ventilation system that keeps air flowing to their muscles. But no one knew how pterosaurs, the first flying vertebrates, powered their wings. A new study in PLoS One concludes that ancient pterosaurs, flying reptiles that lived 220 million to 65 million years ago, did much the same, with a mobile rib cage and a system of air sacs distributed throughout the bones to help move air around."Note as always there are dissenting opinions:
"The researchers also studied the air spaces in pterosaur bones and concluded that they were associated with air sacs, arranged in patterns similar to those seen in modern birds. The bigger the pterosaur, the more air sacs, just like in modern birds. The air spaces help oxygen circulate and probably also made bones light enough for flight."
"But matching anatomy in pterosaurs to modern animals may be misleading, says Jaap Hillenius, a functional morphologist at the College of Charleston in South Carolina. Pterosaurs left no descendants and are only distantly related to birds. It's possible that the new study is correct, Hillenius says, but he's skeptical. For example, he thinks the model of rib-cage movement doesn't allow enough air for active flight, and that the sternum was not strong enough to support such movement. "Until we find a living pterosaur," there's no way to know for sure—"and that's not going to happen."".
The study itself:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2637988/
https://en.wikipedia.org/wiki/Air_sacs
John Ruben et al. (1997, 1999, 2003, 2004) disputed this and suggested that dinosaurs had a "tidal" respiratory system (in and out) powered by a crocodile-like hepatic piston mechanism – muscles attached mainly to the pubis pull the liver backwards, which makes the lungs expand to inhale; when these muscles relax, the lungs return to their previous size and shape, and the animal exhales. They also presented this as a reason for doubting that birds descended from dinosaurs.[5][6][7][8][9]
Critics have claimed that, without avian air sacs, modest improvements in a few aspects of a modern reptile's circulatory and respiratory systems would enable the reptile to achieve 50% to 70% of the oxygen flow of a mammal of similar size,[10] and that lack of avian air sacs would not prevent the development of endothermy.[11] Very few formal rebuttals have been published in scientific journals of Ruben et al.’s claim that dinosaurs could not have had avian-style air sacs; but one points out that the Sinosauropteryx fossil on which they based much of their argument was severely flattened and therefore it was impossible to tell whether the liver was the right shape to act as part of a hepatic piston mechanism.[12] Some recent papers simply note without further comment that Ruben et al. argued against the presence of air sacs in dinosaurs.[13]
http://pterosaurnet.blogspot.ca/2010/05/another-thing-to-watch-for.html
http://pterosaurnet.blogspot.ca/2014/04/pneumaticity.html
http://pterosaurnet.blogspot.ca/2013/12/respiratory-cycle-of-bird_16.html
https://en.wikipedia.org/wiki/Pterosaur#Air_sacs_and_respiration
A 2009 study showed that pterosaurs had a lung-air sac system and a precisely controlled skeletal breathing pump, which supports a flow-through pulmonary ventilation model in pterosaurs, analogous to that of birds. The presence of a subcutaneous air sac system in at least some pterodactyloids would have further reduced the density of the living animal.[18]Like modern crocodilians, pterosaurs appeared to have had a hepatic piston, seeing as their shoulder-pectoral girdles were too inflexible to move the sternum as in birds, and they possessed strong gastralia.[45] Thus, their respiratory system had characteristics comparable to both modern archosaur clades.
Sauropods, many theropods (including ones you don't think are related to birds) and the maniraptorans also have air-sacs. It is likely that ornithopods did too, although theirs did not penetrate the bones- unlike those of sauropods.
ReplyDeleteThe website SV-POW has excellent coverage of this, should you be interested.
In fact crocodiles have through-flow lungs. So a whole series of animals with no adaptations to flight have "bird-like" lungs and air-sacs.
Are you suggesting that birds developed from crocs? The reason I ask is, I am quite familiar with the argument that crocs have flow through lungs.
ReplyDeleteBut dinos do not.
It does not support the dino to bird idea to say that crocs have flow through lungs.
I have seen others try this bait and switch. I hope you are not trying it.
Pterosaurs have lungs like birds. Dinos do not.
Also you said:
"..the maniraptorans also have air-sacs".
Of course they do. They are birds. Just as I have been saying.
evidence that dinosaurs did have air sacs and flow-through lungs
ReplyDeletehttp://www.ncbi.nlm.nih.gov/pubmed/18825273
"We describe a new predatory dinosaur from Upper Cretaceous rocks in Argentina, Aerosteon riocoloradensis gen. et sp. nov., that exhibits extreme pneumatization of skeletal bone, including pneumatic hollowing of the furcula and ilium. In living birds, these two bones are pneumatized by diverticulae of air sacs (clavicular, abdominal) that are involved in pulmonary ventilation. We also describe several pneumatized gastralia ("stomach ribs"), which suggest that diverticulae of the air sac system were present in surface tissues of the thorax."
Full paper available here:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2553519/?tool=pubmed
"The Miz" - thank you for your contribution
ReplyDeleteI appreciate that you gave us the link and copied and pasted what you felt is the relevant material.
This creature gives me the opportunity to make this point:
The authors say:
"In living birds, these two bones are pneumatized by diverticulae of air sacs (clavicular, abdominal) that are involved in pulmonary ventilation".
This is the trick that I have mentioned before.
The authors of the study present evidence of pneumatization.
However there is NO evidence of a bird-like respiratory system.
Let me say that again:
However there is NO evidence of a bird-like respiratory system.
And yet they go into an extended speculation about how this is related to bird's respiratory system.
I COVER THIS EXACT STUDY AT LENGTH HERE:
http://pterosaurnet.blogspot.com/2010/05/another-thing-to-watch-for.html
I COVER THIS EXACT STUDY AT LENGTH HERE:
ReplyDeletehttp://pterosaurnet.blogspot.com/2010/05/another-thing-to-watch-for.html
If people want an education on the topic of pterosaurs and birds you will find that MANY topics are already covered in the posts I have entered on this site.
You can use the search function to access the material.
In this case, all you needed to do was enter
"Aerosteon" in the search function.
You could even enter "pneumatization".
No, I am not suggesting birds evolved from crocs. I am suggesting all archosaurs had (or have) through-flow lungs. You're still ignoring the sauropods. According to you, evidence for air sacs in Aerosteon isn't evidence for bird-like respiration, and yet the same pneumatisation would be evidence for bird-like respiration in maniraptorans? This is illogical.
ReplyDeleteAdditionally the air-sacs are part of a bird-like through-flow system. No dinosaur had mammalian-bellows like lungs. In fact air sacs (particularly ones that penetrate bones - for obvious reasons) would not function in a mammalian bellows system. So given their extensively pneumatised backbones sauropods must have had bird-like respiration. And no mammal has air-sacs like those of birds- bats don't have hollow bones for example. The airsacs under the skin that you mention in your blog post are also part of the birds though-flow-lung system. Again, more information can be found on SV-POW's excellent website, where they deal with their own criticisms of Sereno's paper. Which do not match up with yours.
The simplest conclusion is that all archosaurs (dinosaurs, pterosaurs, crocodiles, rauisuchians, etc) have this through-flow lung system, and that in pterosaurs, theropods (not just maniraptorans) and sauropods it invaded the skeleton, for a variety of reasons- in most cases to do with lightening the skeleton, without weakening it, something that has advantages even if an animal cannot fly.
A Nonny Mouse please read the post that I mentioned.
ReplyDeletehttp://pterosaurnet.blogspot.com/2010/05/another-thing-to-watch-for.html
And if you are going to make assertions as you have, please support them with references and copy and paste what you think is the relevant material. (I am not interested in debating your opinions).
Before this discussion goes too far, I will say again that people can argue anything till the cows come home. That means nothing.
ReplyDeleteI will not make the mistake of being sucked into that.
I did read your post. Your criticism is unfounded. As for your usual demands to copy and paste and provide references, this is now basic information available in entry level text-books. Like I said, go to SV-POW and look at their extensive posts on pneumaticity. There's more there than I can quote in a single post.
ReplyDeletehttp://svpow.wordpress.com/category/pneumaticity/
One of the authors, Matt Wedel, has also published on this work.
Yates, A.M., Wedel, M.J., and Bonnan, M.F. 2011. The early evolution of postcranial skeletal pneumaticity in sauropodomorph dinosaurs. Acta Palaeontologica Polonica.
http://www.app.pan.pl/archive/published/app56/app20100075_acc.pdf
Wedel, M.J. 2009. Evidence for bird-like air sacs in saurischian dinosaurs. Journal of Experimental Zoology 311A:611-628.
http://sauroposeidon.files.wordpress.com/2010/04/wedel-2009-air-sacs.pdf
That whole paper discusses air sacs in birds, non-maniraptoran theropods, and sauropods. However it was published before the work on the through-flow lungs of crocs was published.
You could just admit that you were wrong, and that through-flow lungs are irrelevant to your hypothesis.
If you are not copying and pasting what you think is the relevant material (which presumably you are looking at) then I am certainly not wasting my time looking for whatever it is you have in mind.
ReplyDeleteYour call.
Umm... all of it is relevant. Would you like Nonny Mouse to copy and paste the whole paper in these comment boxes?
ReplyDeleteActually, its your call. Your the one choosing to remain ignorant of the information available to you.
ReplyDeleteEverything in the second paper by Matt Wedel is directly relevant to this. Much of what they have discussed on the blog is too, but first read that paper. It is all relevant. It is all informative. It is all freely available. I would have to reprint the whole paper to reference what I have in mind, as I have the whole paper in mind. The discussions of avian respiration. The discussion of evidence for cervical, clavicular and four different lines of evidence for abdominal air sacs. Additionally many of the references he cites might prove useful to you. It is all relevant.
Winterhaven, I have heard that excuse before.
ReplyDeleteI think you should stick with something like the dog ate your homework.
I have no problem in copying and pasting relevant material and have been doing so for years. And I have seen many others do it.
A Nonny Mouse posted:
ReplyDelete"Everything in the second paper by Matt Wedel is directly relevant to this. Much of what they have discussed on the blog is too, but first read that paper. It is all relevant. It is all informative. It is all freely available. I would have to reprint the whole paper to reference what I have in mind, as I have the whole paper in mind. The discussions of avian respiration. The discussion of evidence for cervical, clavicular and four different lines of evidence for abdominal air sacs. Additionally many of the references he cites might prove useful to you. It is all relevant."
A Nonny Mouse see my response to Winterhaven.
A Nonny Mouse are you claiming that birds evolved from sauropodomorph dinosaurs?
ReplyDeleteWinterhaven are you claiming that birds evolved from sauropodomorph dinosaurs?
ReplyDeleteNo of course not, and nor is Winterhaven. Try reading what we actually wrote. And Matt Wedel's paper. We are both stating that though-flow lungs and pneumatic bones (which provide evidence of air-sacs as seen in birds) are present in a wide variety of dinosaurs. Air-sacs are likely to be primitive to saurischians, and quite possibly dinosaurs as a group, and through-flow lungs are primitive to archosaurs.
ReplyDeleteIt does not provide evidence that birds are descended from pterosaurs.
Wedel's papers cover sauropods.
ReplyDeleteBut pneumatization does not even necessarily provide evidence of air sacs and flow-through lungs. There are other simpler explanations including one that Sereno was "especially intrigued by".
ReplyDeleteSee my earlier post:
http://pterosaurnet.blogspot.com/2010/05/another-thing-to-watch-for.html
Wedel's papers cover sauropods.
ReplyDeleteI had to waste my time to find that out. Because you folks were unwilling to present that fact. But I know you will now present a whole new bunch of excuses.
Copy and paste material and stop wasting my time.
They also cover theropods (including birds). Read the whole paper.
ReplyDelete"They also cover theropods (including birds). Read the whole paper."
ReplyDeleteCopy and paste what you think is the relevant material.
This is getting absurd.
ReplyDeletePeople refer me to a reference that they think has relevant material. PRESUMABLY THEY ARE LOOKING DIRECTLY AT THAT RELEVANT MATERIAL.
And instead of copying and pasting it, they refer me to the "whole paper".
You folks do not realize that I have been down this road many times before.
People are always trying this stunt.
Here is the relevant parts of what I posted earlier:
ReplyDeletehttp://pterosaurnet.blogspot.com/2010/05/another-thing-to-watch-for.html
(6) The origin and evolution of avian air sacs may have been driven by one or more of the following three factors: flow-through lung ventilation, locomotory balance, and/or thermal regulation."
http://newswise.com/articles/view/544722/
"Sereno, a National Geographic Explorer-in-Residence, said he is especially intrigued by heat loss, given that Aerosteon was likely a high-energy predator with feathers but without the sweat glands that birds possess. At approximately 30 feet in length and weighing as much as an elephant, Aerosteon might well have used an air system under the skin to rid itself of unwanted heat."
This is also relevant:
http://newswise.com/articles/view/544722/
"In sauropods, pneumaticity was key to the evolution of large body size and long necks
It is only because the researchers have it in mind that birds evolved from dinos that they put forward this dubious idea that pneumaticity is related to imaginary air sacs and imaginary flow-through lungs.
If they did not have that in mind they would have all agreed that it was for thermal regulation and moved on.
And people here could have learned all this simply by putting Aerosteon or pneumatization in the search function on this site.
ReplyDeleteNo. Pneumaticity does imply air sacs. And air-sacs mean through-flow-lungs. No imagination is required. Only a refusal to engage with the facts. As Wedel's paper indicates. As does the Aerosteon paper. If they had read the actual paper I linked to they would have learnt far more. Through-flow-lungs are a pre-requisite for air-sacs. Air-sacs are a pre-requisite for poscranial skeletal pneumatisation.
ReplyDeleteWedel then goes on to discuss the detailed anatomy of the PSP of sauropods and theropods. You need to have through-flow lungs for air-sacs to work. You need air-sacs for PSP to occur.
You've also misread your quotes. In the first Sereno is asking why air-sacs evolved, he's not relating the existence of air-sacs in theropods (conclusively shown by PSP, as demonstrated by Wedel and others) to the origin of birds, but to why birds have them in the first place. If you think that birds evolved from pterosaurs then you need to explain why pterosaurs evolved them. And you're back to ideas about thermoregulation, locomotory balance, and the efficiency of through-flow-lungs. Unfortunately all pterosaurs have PSP, and there are no protopterosaurs that can shed light on this problem.
Sauropods have PSP and this is independently evolved from theropods and pterosaurs. Therefore they all had air sacs. (Most likely the saurischians inherited them from their LCA. Perhaps pterosaurs evolved them independently?) All must have had through-flow-lungs. Alligators also have through-flow-lungs. Therefore through-flow-lungs are likely to be primitive to archosaurs. And another piece of "evidence" for your ideas is shown to be nothing of the sort.
A Noony Mouse, I appreciate that you are taking the time to respond. Could you take an extra 15 seconds and copy and paste the material you are looking at that leads you to form these opinions you are expressing?
ReplyDeleteThat would be great.
You posted:
"Unfortunately all pterosaurs have PSP"
That is not "unfortunate". It is one of the strong pieces of evidence supporting the pterosaur to bird theory.
It is "unfortunate" only from the point of view of the discredited dino to bird theory.
By the way, what you are doing is what I mean by "spin". You try to take a strong piece of evidence on behalf of the pterosaur to bird theory and spin it as a disadvantage.
I have not been pointing out all your attempts at spin but I certainly notice them.
Let me remind you that I have seen others who are much better at spin than you.
Tell you what A Nonny Mouse. If you decline to support your posts with references with copied and pasted material, I will simply not post them.
ReplyDeleteThis is not a site for people to come and post their unsupported opinions.
Here is a question that I do not recall ever seeing.
ReplyDeleteIs there any disadvantage to having a flow-through breathing system, including air sacs, in a land based creature?
Can anyone think of any disadvantage for a land-based creature to have a flow-through breathing system, including air sacs?
ReplyDeleteHere is the disadvantage.
ReplyDeleteOn the ground there is fighting. One animal fights another.
A creature with air bags would be easily defeated by an opponent who attacks those areas where the air bags are. And they would present a nice big target.
Having those air bags damaged in a fight would be disastrous as it would immediately interfere with the breathing.
Birds can get away with having air bags because they flee from fights. They do not go in for hand to hand combat like dinosaurs did.
Dinosaurs did not have air bags.
The other consideration is the advantage of the flow-through breathing system. It is ideal (essential) for a creature that needs to make a sustained muscular effort over many, many hours. Obviously that is a requirement for a bird that is making a great muscular effort when it flies. Think about those migrations.
ReplyDeleteLand-based creatures do not have that requirement. They need to make great efforts from time to time - think about that fighting.
But then they rest.
Birds NEED air sacs. Pterosaurs NEEDED air sacs (and everyone agrees that they had them). Dinosaurs do not NEED air sacs.
I came upon this reference from Harry Seeley:
ReplyDeletehttp://www.freefictionbooks.org/books/d/23536-dragons-of-the-air-by-h-g-seeley?start=19
PNEUMATIC FORAMINA IN PTERODACTYLES
[Illustration: FIG. 15. HEAD OF THE HUMERUS OF THE PTERODACTYLE ORNITHOCHEIRUS
Showing position of the pneumatic foramen on the ulnar side of the bone as in a bird]