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Re: Ornithodira, breathing with long necks
Does that mean they do not believe the neck air-sacs could act as an
alternate exhaust route to the trachea. I do not know if any living
animals (most likely with long necks) have an alternate path. Even if they
do not, why could in not be possible in Sauropods?<
As in, one path for exhaling, and the other for inhaling? It seems to me
that it would be hard to take all the air inhaled through the nostrils down
to the lungs before the lungs needed to exhale the waste gasses. It seems
like the two would contradict each other, and you'd end with a dead
sauropod. However, my understanding of respiration is limited, and so is my
knowledge of sauropods. Maybe one of the sauropod guys or gals onlist could
If the outside air is warmer than the animal, evaporative cooling is about
the only means of cooling available!<
This assumes that the outside air is indeed usually warmer than the animal.
In endothermic homeotherms, the mean external temperature is a good deal
cooler (usually) than the animal. Hence, we aren't sweating all the time.
Using moisture to cool the head seems more probable.<
What of the rest of the body?
Turbinates are more likely (to me) heat retention improvements for animals
whose endothermic ancestors spent some time in cooler climates as they
But both the Permian and Triassic were characterized by very very limited
ice caps at the south pole, and a vast desert in the interior of Pangea.
There would be no real cooler climate for these animals to hang out it, from
what I understand. The world was pretty hot and dry.
How would they get pressurized?<
I'd assume through repiration. We are dealing with large lungs here.
Could they bend the neck? Of course, this use would preclude using them for
I'd assume that by reducing the pressure in the sacs, through repiratory
controls, the neck could vary in stiffness. I don't see how this precludes
them for use in breathing. How else would the air get there, and pressure be
Was it big enough to allow endothermy?<
The question is, do air-sacs always equal endothermy. And what is this
threshold that you are talking about here?
Why can?t efficient lungs, a 4 chamber heart, an upright gait, and warm
external air mean high, long duration activity levels and rapid growth
could not be achieved?<
I'm confused by this statement.
As much as I want to believe all dinosaurs were endothermic like mammals, I
can?t convince myself that it is the only explanation without answering
While the evidence does seem to point towards endothermy, I don't think I
would agree that it would be a mammalian style endothermy. Rather, if
anything, it would be avian, or primative avian, where their resting
temperature can drop a good deal.
Humans managed flight using machines made by their free hands? ground up
according to the latest quarters (but not chasing after insects).<
But not biologically. And there has been no pressure selecting towards
hominid flight, in any case.
As for as pterosaurs. If they had a bipedal gait, I would doubt it was
very good. Otherwise, there would probably have been many later flightless
Not really. Why would flightless pterosaurs evolve, when most to all niches
are filled on land by dinosaurs. The likely place for flightless pterosaurs
would be islands, and the only place I can think of off the top of my head
to find these fossils, would be California, where island terranes were being
accreted onto the continent. Besides, why could their be quadrapedal
HP Gregory S. Paul is onlist, so if he hasn't already done this today (my
mail server is overloaded), he will surely tear any argument that
sauropods didn't need high metabolism to very, very small pieces.<<
Indeed. I find HP Paul's Dinofest paper most intriguing.
In his Predatory Dinosaurs of the World, he essentially stated that larger
endothermic animals had lower metabolic rates per pound than smaller
But, predatory dinosaurs were nowhere near the size of the largest
sauropods. But, I'll let HP Paul fill in the details, since I believe he has
a greater understanding of this than I do. But I too recomend his 1994
Why would an extremely large animal generate lots of internal heat when he
could not get rid of it?<
Why couldn't it? With a large surface area, facilitated by etremely long
legs, neck and tail, there was plenty of surface area to volume to dump
Sauropods may have been endothermic (I believe they were), I am just
looking for a reason why a large animal (or small for that matter), with a
4 chambered heart, and birdlike lungs would have to have been endothermic
and homeothermic to be active or grow fast if his body was warm.<
It doesn't need to be. But, it is more likely, I think. Where is the
evidence for the avian lungs and 4 chambered heart, though?
Student of Geology
Northern Arizona University
P.O. Box 20840
Flagstaff, Az. 86011
"A _Coelophysis_ with feathers?"
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