Re: Resources, energetics and dinosaur maximal size

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

Jura schrieb:

>  McNab goes further with this, by showing that a hypothetical sauropod
>  with an "average lizard" metabolism (i.e. the metabolism of a sit and
>  wait iguanian), would "need" to grow to 330 tonnes in order to
>  consume the same ammount of calories as a large African elephant
>  (_Loxodonta africanus_). That no sauropod comes close to this
>  estimated size, suggests that sauropods had higher FMRs than this.

Fine so far...

>  If they were given a mammalian
>  metabolism, and concomitant FMR (as detailed in the paper) then a 56
>  tonne _Brachiosaurus altithorax_ would have to digest some 561,000
>  calories a day. This is asking a lot for plant productivity of any
>  time period.

A 56-tonne *Brachiosaurus altithorax*? OK, a fifteen-tonne one might be 
too light despite all air sacs, given the reported existence of 
ten-tonne and apparently even thirteen-tonne elephants. So let's say 
twenty. OK, thirty. But fifty-six? In an individual that's not grossly 
obese? Seriously?

Never forget that Godzilla is right: size does matter.

>  It is under this assumption that McNab posits that sauropods would
> have been unlikely to have sustained a mammalian level FMR.

The body masses, too, are assumptions.