[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: [Re: ... vs energy deficient gigantothermy (boo hiss)]



> I have no problem agreeing with that, but it does leave me with a bit of a
> quandary; why is the lack of multitonne birds attributed to environmental
> factors (e.g. no big game, died before their time) while the lack of
> multitonne reptiles (excluding dinosaurs) is attributed to their
physiology.
> Did one ever stop to think that the reason why _M.prisca_ never got any
bigger
> was because it was large enough to be an effective predator of moas.

No moas in Australia, never.
Well, this may be true for *Megalania*, there is only negative evidence in
this case. However, why didn't diadectomorphs or pareiasaurs (or, for that
matter, dicynodontids etc.) reach sizes over 1 t or so?

> Anyhoo, I'm in agreement with HP Matt Bonnan. There's more to meets the
eye
> here than simply physiology.

Sure.

> > > From: Ecology of the Komodo Monitor
> > > "Normal walking and searching is carried on at a speed of
approximately
> > > 4.8 km/hr (our observations agree with those of Lederer, 1942)."
> > > Work Auffenberg cited:
> > > Lederer, G. 1942. Der Drachenwaren (_Varanus Komodoensis_ Ouwens).
Zool.
> > Gart. (Leipzig), (n.s.) 14 (5/6):227-244
> >
> > OOC -- you trust a paper from 1942 that is apparently based on
> > observation in a zoo? This is so old that I didn't even know that The
Beast
> > was ever called "Drachenwaran" (the e must be a typo) in German!
>
> No, I never read it. I was only citing the paper that Auffenberg cited,
which
> agreed with his assessment of ora speeds, which were taken in the wild.
This
> was in response to GSP's original comment that statements in the
literature of
> 5km oras were wrong (admittedly this does agree with his statement, but
flat
> out disagrees with his statement that they only "plod" along at 1-2km/hr).
>
> So what does "Drachenwaran" [...] translate to?

Dragon monitor/goanna. Quite fitting; today it's called Komodowaran.

> (Drachnwaran?)

Closer to actual pronunciation (if you make that n ng), but regarded as
horror by German orthography :-)

> > > Yes, and these mammals also have anatomical "cheats" that allow them
> > > to hold up their large bodies with very little muscle use (e.g. the
> > > locking mechanisms of elephant and ungulate legs). A reptile with
> > > equivalent "cheats" wouldn't find it so hard to hold itself up either.
> >
> > This works only in _standing_. Not in walking.
>
> True, but free oneself from the aerobic problem of lung compression while
> walking and, possibly, lower the cost of locomotion and there should be no
> problem.

Locking mechanisms, AFAIK, only reduce the cost of standing, not that of
locomotion and lung compression during locomotion.

> Incidentally, since we are talking about sauropods, would it not make
> more sense to have these "cheats" in place if one isn't going to be
walking
> half as much as they will be standing?

Sure. Just that these are AFAIK no use for walking, and they did walk,
however much or little.

> > Turtles are quite immune to predation, aren't they?
>
> I don't know; turtles are weird not only phylogenetically, but
ecologically
> and metabolically as well.

They're far not that weird phylogenetically. According to someone who does
molecular systematics here at the university, the molecular trees that put
them next to crocs result from the only (badly) known turtle 18S rDNA
sequence, and this has evolved so fast that artifacts like long-branch
attraction blur the picture beyond any recognition. He is said be surprised
that turtles didn't come out close to mammals based on such data.
        You can forget Parareptilia again, it's a junior synonym of Anapsida
:-) (well, let's wait which will be defined first under PhyloCode, which
won't be retroactive).

> Yeah, _Geochelone nigra_ has reached some pretty
> successful sizes and previous giant tortoises were even larger, but the
> chelonian shell has been around for some 230 million years. That's an
awful
> lot of time for predators to find ways around it (tiger sharks saw through
> turtle shells, alligators crack'em open, certain raptors drop them from
high
> heights on rocks). How they can get away with all this and still attain
large
> terrestrial sizes escapes me.

OK: more immune to predation than most other animals (when adult).