Re: Resources, energetics and dinosaur maximal size

[Graydon <oak@uniserve.com>]

On Mon, Jul 27, 2009 at 09:33:15AM -0700, Jura scripsit:
> McNab assumes Mesozoic plant communities were about as productive as
> that of those in the East African plains (obviously a simplification
> on his part, but a necessary one. Probably best to look at it as the
> "average" Mesozoic plant community), and does consider Hummel et al's
> recent work on fern nutrition. Using Hummel et al's data, Mesozoic
> plant communities would come off as less than, or equal,
> nutritionally, to those of extant plant communities. It is under this
> assumption that McNab posits that sauropods would have been unlikely
> to have sustained a mammalian level FMR.

But that has almost nothing to do with it. (Does it?)

In modern assemblages of terrestrial mammalian herbivores, grasslands
introduced a bias in favour of artiodactyls, who have a "better" -- more
complete, more efficient -- digestive system than perissodactyl hind-gut
fermentation.

The very best artiodactyl efficiency remains not that blessed good,
however; dried, *all* artiodactyl dung burns with a hot flame.  There's
a lot of energy left in there when your bovid, cervid, camelid, etc. is
done with it.  (Never mind the whole "the dung beetles would starve" end
of the argument.  There's almost certainly a way to get leftover energy
out of the resulting mass of beetles per kg of dung.)

All you have to do is postulate a non-bacterial cellulose digestion
mechanism, and all this reaching after energetic boundaries collapses.
Since *something* drove sauropods to evolve immense size on very coarse
fodder, including -- because there wasn't anything else available, and
there's no indication of either parental care or ontogenetic alterations
in feeding mechanisms -- during the rapid growth phase from hatchling to
probable sexual maturity, I don't think this is a possibility that can
be waved away by pointing to mammalian analogs.

-- Graydon