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Re: Physiological Adaptations of the Dinosauria (long)
From: Waylon Rowley
Subject: Re: Physiological Adaptations of the Dinosauria (long)
Hm. Possible, though improbable. But I think if *Sinosauropteryx* would
compress its...errr...protofeathers close to the body, this would still
allow quite little heat exchange. The "downy covering" was quite dense. >So
I'd still say, if protofeathers aren't direct confirmation for >endothermy,
they come very, very close.
Oh! Seems like Ruben uses a different definition :-/ . Horner has
>suggested that hadrosaurs used the mode you describe and has called this
"mesothermic". However, he thinks that only really big adult dinosaurs
Mesothermic could be misconstrued as being a metabolic condition between
bradymetabolic ectotherms and tachymetabolic endotherms. But I like the
word, so i'll use it....heheheh
On sauropod spines:
If they were sufficiently vascularized (which I don't know), yes.
>Stegosaur plates were surely good for this purpose.
I would think a sauropod osteoderm/spine would be highly vascularized like
one of the dorsal crocodilian scutes. I've also heard that stegosaur plates
are highly vascularized....good example.
I do, based on the article I cited yesterday (or today, depending on >where
you are...), which says that a heart that can sustain a sauropod >has alone
a greater energy demand than a hypothetical ectotherm of >sauropod
That is, assuming we know how a sauropod heart functioned, or if it had some
adaptation like that of giraffe (carotid cuffs). For all we know, they had
muscular contractions along their arteries that pushed the blood up (or some
equally wild system).
This argument has been raised quite often, and the only counterargument >is
that this has never happened elsewhere... Well, I think the >plesiomorphy
for archosaurs or at least crurotarsans is the liver->pumped lung that
Ruben imagines for dinosaurs (LOL) which allows >greater activity for
ectotherms. I don't think one can explain the >success of big runners (some
of them probably bipedal or semibipedal) >like ornithosuchids, rauisuchians
(however paraphyletic they may be) >and early crocodilomorphs if they all
were normally cold-blooded.
Indeed, crocs can gallop, and I've even read that if you manage to >scare a
croc, it may run away on its hindlimbs!
(tries to imagine a T. rex liver pump....with no success)
About your comment on crocs: that's precisely the reason why I suspect we'll
soon see Steve Irwin (a.k.a. "The Crocodile Hunter") in the obituary section
On the isulating layer of Iridium in the atmosphere, you said:
Yes. At first it became terribly cold and dark for some months, and >later,
when sunlight got through again, temperatures rose by 10 °C for >100 or
1000 years because the rock at the impact site (as well as the >global
forest fires) gives lots of carbon dioxide when vaporized. Of >course, the
scenario is more complicated, e. g. it involves terrible >acid rain...
I wonder how much stored heat in the ocean would rapidly transfer into the
colder atmosphere after the impact....Maybe that killed off the marine
reptiles? I don't see why global cooling would kill off the dinos, so they
may have lived through that stage, but were later killed off by the heating.
Flying rather heats, because it is such a demanding exercise.
BTW, I've heard of 42 °C, and probably even more.
Flying *heats*....that's right. D'oh!
Lots of new books and papers show that this is a myth based on poor
statistics (the Signor-Lipps effect). Recently, someone found a
*Triceratops* skull 1.8 m below the K-T boundary, and hadrosaur >footprints
have long been known from 37 _cm_ below the boundary, so the >3-m-gap is
That's another thing I wanted to bring up. What role could the ceratopsion
frill have played in cooling blood that was directed toward the gigantic
narial fossae of these beasts? It seems like a good theropod crest analogue.
And BTW, Mickey Mortimer has pointed out that some of the more basal
ornithischia (and some more andvanced forms like stegosaurs) either reduced
the size of their antorbital fossae or lack it entirely. I considered that
when I was writing my article, and one possibility is convergent acquisition
of endothermy or a reversal. I'm not a predentate lover, and I don't know
too much about their nasal passages besides what i've seen in The Dinosauria
(Weishampel et. al.), but I do think that if we going to look for RT's in
any dino, it should be these guys....they may have found another way to
recover moisture. And again, I apologize for the extra e-mail.
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