[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Terramegathermy in the Time of the Titans (not so long...)
> You said:
> "I wouldn't consider "hyperanaerobiosis [...] works only for a few
> and is followed by toxic effects" weasel words: they say quite clearly
> while hyperanaerobiosis is perfectly fine for sit-and-wait activities, it
> can't be sustained for e. g. migrating."
> But as pointed out by Darren Naish recently on the list, many
> organisms do migrate vast distances. I'm not arguing for hyperanaerobosis
> in dinosaur muscles, just that P&L are setting up a false dichotomy: if
> dinosaurs were not like modern reptiles, they had to be like mammals and
> birds. Not necessarily so. And even then, WHICH mammals and WHICH birds?
> Placental mammals? Marsupial mammals? Montremes? Ratites? Non-ratites?
> All of these tachymetabolic endotherms have a wide metabolic scope.
P&L didn't write that no ectotherm migrates. They wrote that no land reptile
migrates (therefore monarch butterflies and land crabs* are irrelevant), and
imply that far-migrating land-living tetrapods must be tachyaerobic.
Therefore I'm interested in how far rattlesnakes migrate, and how long it
* HP Kean Stump has been so kind as to send me
http://www.tiskita-lodge.co.cr/activities/land-crabs.shtml. There it says:
"Migration of ovigerous females to the sea to release larvae can be as short
as the distance from upper beach to surf, as in ghost crabs, or as long as 8
km in some upland crabs." This is not much, and comparable to the migrations
of toads in the mating season. Some dinosaurs are supposed to have migrated
from Alberta to Alaska and back every year, and sauropods are supposed to
have walked away after having emptied a region of edible plant parts, like
gnus in today's Serengeti...
> You said:
> "But being big requires a heart that is not only four-chambered but
> also _big_ and therefore can't be financed by bradymetaboly (see Table 1),
> therefore, being big requires being tachymetabolic, P & L write."
> Yes, I understand, but do you understand that the large, four-chambered
> heart probably came BEFORE endothermy?
Four-chambered, yes. P&L don't dispute this. But no crocodile has a heart
that is so oversized as needed for a giraffe or sauropod, and P&L calculate
that no bradymetabolic animal could finance such a heart. "Size does
> It does not necessarily follow that
> therefore if you have a big, four-chambered heart you are automatically a
> tachymetabolic endotherm.
If it is big, really big, not the relative size of a human heart, then,
according to P&L, it does necessarily follow that you are tachymetabolic.
Nothing said about endothermy, but the heat produced by tachymetaboly will
probably suffice to sustain endothermy.
> Besides, things are not so black and white. Reid
> (1997, in the Complete Dinosaur) has even suggested that dinosaurs had an
> intermediate metabolism and were "failed" endotherms. Dinosaur physiology
> is a very complicated area of study because so much of the evidence is
> indirect, and we must be very careful about the conclusions we draw.
All I remember of reading that article (once, long ago) is that I found it
unconvincing :-] . Can someone tell me what Reid meant and why?
> If you haven't, I recommend reading the articles and books of Dr. Knut
> Schimdt-Nielsen. He writes fascinating discussions about animal size,
> metabolism, and physiology.
Where can I find these? Never seen the name...
> You said:
> "Good luck [on your Ph.D. defense next week]! What's the topic?"
> Sauropod locomotion. =)
I should have guessed... :-)