Re: [Re: [Part 2: Terramegathermy (very long, too)]]

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

> > Not much. Mainly the argument from generational turnover: *Deinosuchus*
> > needed 50 years to reach 10 m. If a sauropod would already have been 100
> > years old when reaching _adult size_ (recent articles say 10 years based
on
> > histology), the populations would have been endangered all the time, and
the
> > fossil record would look different (contain far, far less adult
sauropods
> > and more younger ones).
>
> Personally I have my doubts about the _Deinosuchus_ study (i.e. are
osteoderms
> reliable indicators of bone growth? Why not long bones or vertebrae?)

No idea... maybe none are known...

> As for the sauropod pop, would we find more young? Adults have more time
> friendly bones, young bones break easy and would have less of a chance of
> fossilizing.

I guess we would find more subadults and even less adults. This may,
depending on taphonomy, not even be falsifiable... :-(

> I mean how many young _Deinosuchus_ fossils do we have?
>
> _Megalania_?

No idea...

> > P&L suggest why -- because the populations of adult animals of sauropod
> > size are very small, they must have crashed from time to time, leaving
the
> > young alone. This is a problem for mammals and many birds, which depend
> > heavily on their parents.
>
> So then, they are not advocating sauropod parenting?

Not much. They think megadinosaurs were more r-strategists than megamammals.
This may offer a reason (if any is needed) why theropods often approached
but apparently never exceeded 15 m and why no flightless birds have come
close to even 1 ton (though no birds probably had the time to evolve
this...). Juvenile tyrannosaurids don't look cute (long snouts...), which
has been regarded as evidence they were quite independent from their
parents.

> > > Sauropods [...] never dealt with temperatures as extreme as
> > > those the leatherback faces.
> >
> > The other way round, as HP Randy Irmis has pointed out.
>
> Okay so then *most* sauropods didn't deal with this type of cold
environment.
>
> Better?

No... unless polar sauropods evolved a different metabolism from others
several times.

> > > Auffenberg is his 81 study of _V.komodoensis_ states that "adults may
> > > move as much as 10km/day..." Now, barring the fact that this is yet
> > > another island species I'm using, that is still a pretty hefty
distance.
> >
> > This is becoming more interesting, but it is still much less than 2 -- 5
> > km/h...
>
> I'm not sure I followed your statement here. Care to elaborate?

I was assuming that the monitors walk constantly for several hours (10 hours
gives 1 km/h, 5 hours gives 2 km/h...). May be naive... :-]

> > For how long can a Komodo monitor walk? An hour? :-/
>
> Unsure; oras probably don't make very good test subjects for treadmill
runs,
> so I wouldn't be surprised if no such endurance study was done on them.

Sounds convincing...

> Auffenberg does mention chasing an ora on a motorcycle for .5 km. But, the
> animals was doing 14 km/hr at the time.

Cool!

> As for the carnivores, Auffenberg himself, mentions that
> ambush predators seem to grow to very large sizes. This could explain the
> large theropods [...]

I disagree. Tyrannosauroids at least are built a lot like runners, and quite
different from *Pristichampsus rollinatii*.

> > > Great, now as long as the prey item doesn't make any sharp turns
> > > _T.rex_ will be set ;)
> >
> > I don't understand this...
>
> Just making a jab at the pursuit hunting _T.rex_ hypothesis. Biomechanical
> studies on large theropods seem to indicate that they couldn't make sharp
> turns. This would be a problem for a pursuit hunter if the prey keeps
zigging
> and zagging. Now if one was an ambush hunter...

I don't think anything the size of *Edmontosaurus* or *Triceratops* can zig
& zag, at least not faster than *Tyrannosaurus*...

> > > Much of which I can certainly agree with; I just don't see why you
> > > need to shove them into the inefficient realm of tachymetabolism to
> > > achieve this.
> >
> > Hm. Considering that tachymetabolism has not been selected against in
> > birds, mammals, and others, it must have some advantage...

By this I meant, if early birds were bradymetabolic, why didn't recent birds
keep that efficient adaptation?

> That tachymetabolism is only found in birds and mammals

among tetrapods

> seems telling to me
> too.
>
> Perhaps once one goes forward they cannot go back.
>
> Does anyone know if naked mole rats have truly dumped their L.C.
endothermy?

I don't know, but I don't think so. AFAIK they just have burrows instead of
fur.

> > 2. From TV observations (not field observations, though...) I claim
their
> > predator/prey ration is much higher than that of tigers. There are just
lots
> > of them.
>
> From: Behavioral Ecology of the Komodo Monitor.
>
> Though there is great disparity in comparing the values for oras and the
large
> mammalian predators, when the latter are considered in terms of the
> porportionate difference in predator size and waste percentage of prey,
the
> disparity is not nearly as great. Thus, though the size ratio of an adult
ora
> to an adult tiger is 1:3, the ratio of the pounds of ungulate prey
required
> per year for each is 1:19. When percentage waste is considered it is 1:15
and
> when poportionate predator size is considered it is 1:5.
>
> As I said...

These numbers fit my above claim, IMHO...

> > Not bad for a damned good reptile :)

Still not good enough for a dinosaur! =8-)