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Re: Battle of the titans: terramegathermy (hooray) versus gigantothermy (boo hiss)



Sorry for any cross-posting...

[...]
> it is not yet certain whether the super moniter
Megalania was fully terrestrial).

Well, I'd say that the semiaquatic niches were already occupied by crocs,
and all other varanids are terrestrial, aren't they?

> [...]
> (Nor are migrating flying
> insects pertinent since all over 1 g are tachyaerobic endotherms with
> exercise energetics as high as those of birds.

Just OOC -- so they are bradymetabolic, tachyaerobic, endothermic and
poikilothermic?

> Bradyaerobic
> land giants would therefore at best be slow, and unable to move very far.
>     That's if they would work at all. Because bradymetabolic animals
> inherently have low capacity central organ dependent respiro-circulatory
> systems, they cannot oxygenate and feed large, high aerobic capacity sets
of
> muscles, so they are inevitably bradyaerobic (ergo, all reptiles have
> relatively small leg muscles, anchored upon very short ilia in the thigh).

Just for the record -- *Eudibamus* has _tiny_ ilia, just a bit longer than
the femur is broad craniocaudally, if I interpret the photo correctly.

>     It is questionable for inherent circulatory reasons that others have
> discussed whether a high pressure, truly four chamber heart is compatible
> with bradymetabolism. Conversely, bradymetabolic organs probably cannot
> support a heart powerful enough to produce high pressures. Because
reptiles
> have only low pressure hearts, they are all low slung even when large.

There are illustrations of the pareiasaur *Scutosaurus* with vertical legs
(at first I thought it was an ankylosaur). Is this incorrect?
The mounted *Bradysaurus* skeleton in the museum here sprawls, anyway.

> Mesoschian proto/dinosaurs - Lagosuchians, eoraptors, staurikosaurs,
> prosauropods have ilia whose length is higher than measured in reptiles
even
> the semi-bipedal ones, but shorter than those of birds and mammals. This
> means that they were intermediate in terms of leg muscle mass and exercise
> energetics.

Muscle mass, yes, but when I look at my own legs... I seem to have
proportionately far less leg muscle mass than most other mammals, no?

> The limited leg musculature also appears ill suited for gigantism.
> It is correspondingly interesting that none of these archaic dinosaurs
> exceeded a tonne or two in mass (some prosauropods).

How heavy, do you think, was the AFAIK 12 m long *Euskelosaurus*?

> [bone isotope data
> suggests that a fairly high latitude armored against attack even when
> immobile ankylosaur may have hibernated through the dark winter]).

1. ... if diagenesis...
2. Where was it found?

>     There is currently nothing in the nature of gigantic longoschian
> dinosaurs that indicates that they were not tachymetabolic tachyaerobic
> endotherms that had completely diverged from the reptilian pattern. Does
not
> mean that they were all exactly like birds and mammals in their
> thermodynamics, but they were much closer to them than to reptiles. This
> further contradicts speculat

Did you intend to continue? :-]