Re: Fwd: Re: New Study, T rex Could've Been A Scavenger

[David Marjanovic <david.marjanovic@gmx.at>]

> >> [...] a large bradymetabolic 
> >> animal can do just as well as a large tachymetabolic one. 
> > 
> >"Large" being the teeny tiny Komodo monitor. 
> 
> ==================================== 
> 
> Large enough to put it on par with some of the large cats (and canids); 
> all of which have been scaled up to be compared with dinosaurs before. 
> [...] 
 
Okay. But while GSP has done the calculations that indicate that an 
endothermic sauropod would not overheat, and that simply because of its 
size any sauropod needed a huge heart the metabolism of which was above 
the resting metabolism of a "reptile" the size of that sauropod, in short, 
while there is evidence that bradymetabolism can't be extrapolated to such 
sizes for terrestrial animals, there is so far no evidence that 
tachymetabolism can't be extrapolated either. 
 
> -------------------------------------- 
>  
> And I haven't read a rebuttal  
> >to HP GSP's idea that bradymetabolic animals are simply incapable of  
> >growing as fast as big dinosaurs did (remember our last discussion).  
>  
> ========================================== 
>  
> Considering the amount of studies done on non-avian/mammalian growth 
> rates, this seems to be more of an assumption on GSP's case. I did give  
> mention to the speedy growth seen in certain pythons and monitors. 
 
How speedy? 
 
> Then there are squid, which have one of the fastest  
> growth rates of any living creature studied. 
 
Sounds interesting. But then they don't have hard parts to build up (apart 
from the beak), nor a lot of muscles (they don't need to support their 
weight), so their growth should be cheaper than that of a terrestrial 
vertebrate. 
        Are the fast-growing fish as well ossified as the slow-growing 
ones? 
 
> >[...] an elephant still needs big  
> >ears, despite having lower metabolic rates per mass than a mouse.  
>  
> ============================================== 
>  
> Ah, but as Spotila (1980) mentioned on this; is the fact that an 
> elephant's MR is only slightly higher than a reptile of equivalent size 
 
Is that a fact? I knew about e. g. sea cows, but elephants? 
 
> the result 
> of a requirement for this MR, or an evolutionary holdover (i.e.  
> automatic endothermy is hard to get rid of once evolved)? 
 
Then who says endothermy isn't plesiomorphic for dinosaurs? 
 
> ------------------------------------------------  
> >> (which makes sense, if the entire point   
> >> of being tachymetabolic is just to keep  
> >> warm).   
> >  
> >Well, it isn't. Who said it was?  
>  
> ========================================= 
>  
> Bakker, Ostrom and many others in passing. 
 
Sorry, I meant within the last few years. Of course the effect is real, 
but it's only seen as a useful a posteriori side effect anymore. 
 
> ------------------------------------ 
>  
> ..., but endurance looks like a good idea, as does brooding.  
>  
> ========================================= 
>  
> As I mentioned previously, endurance has a false correlation to 
> tachymetabolism. Yeah, if one compares all extant reptiles to all  
> extant mammals and birds, then one should get a noted correlation  
> between tachymetabolism and 
> increased endurance, but if one adds fish and insects into the mix 
 
Fish swim. Swimming is a lot cheaper than walking, as GSP quantified (any 
movement of the body moves you through water; a leatherback turtle's 
metabolism could not sustain any reasonable walking speed). Insects are 
tachyaerobic, and at the same (high) speed flying is more efficient than 
walking. 
 
> [...] a strong correlation to [...] flight and 
> endurance 
 
True. 
 
> As for brooding, I could bring up those pythons again. 
 
They are part of the argument that constant high metabolism is good for 
brooding. :-) 
 
> ----------------------------------------------- 
> >     Apart from that gigantothermy doesn't work for pretty much  
> >anything with a shape different from a sea turtle's.  
>  
> ============================================== 
>  
> Is not gigantothermy anything more than just scaled up inertial 
> homeothermy? 
 
Sure. Which is why I mentioned it even though you didn't mention the word. 
Anyway, the real point of this is that gigantothermy doesn't give you 
chemical energy, while endothermy does, and for muscle contraction you 
need ATP. 
 
> I do have aerobic endurance info on varanids though (big surprise >:) 
>  
> Studies on varanids by Bennet (1972) showed that at mammalian body 
> temps, aerobic scope was essentially the same.  
> They incur oxygen date no faster 
> than mammals, and repay it just about as quickly. 
 
Is that about endurance? Or just about how high their exercise metabolism 
can rise and how good their remarkable respiratory system is (in short, 
they aren't really bradyaerobic)? 

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