Re: Regarding Spinosaurus

["Fam Jansma" <fam.jansma@worldonline.nl>]

>Probably not; there are extant "cold-blooded" reptiles today with sails and
none of them use their sails for any thermoregulatory boost (they can't as
they all live in environments that aren't very conducive to solar heating).
In all cases, sexual selection seems to be their big reason to evolve.
Furthermore all large reptiles lack any form of heat acquiring device. Since
they are so large, they retain the heat acquired during activity and most
(e.g. Komodo dragons and large crocodiles) rarely drop more than a degree or
two throughout the day. They are essentially "warm-blooded" at this point.
>
I don't doubt the fact that the sail was used for intimidation, but the
sails you mean are fleshy and not supported by bone. It's also hard to think
of a example of an extant reptile with a sail sticking out of it's back
that's around the length of it's hindlimbs. Alright, the scale has to be
altered, but when you evolve this big sail, you have to have a practical use
for it and not only for impressing other members of your genus.
>
>Of course since sails evolved in so many different dino types at that
period in time (and at that latitude) I do think that it probably did play a
thermoregulatory role. Though it was probably used more as a heat dump
rather than as a heat capturer.
>
The problem is that if a Ouranosaurus dumped it's heat, it takes some time
to do so, leaving it open to attack for a hungry Carcharodontosaurus or
Spinosaur. Evolution has always been about survival, not suicide.

>Furthermore many small tropical reptiles have developed a variety of
different means to avoid large thermal loss (e.g. shunting, burrowing and
selective sleeping positions, sociality) and rarely need any real long
"activation" period in the morning.

Carcharodontosaurus didn't have a sail, so if he had to avoid heat-loss, he
dug himself in to the ground? Can't really say it is possible with it's
short frontlimbs and huge size, but another question revolving about thermal
regulation: if all these animals in the Sahara evolved these sails,
Spinosaurus, Ouranosaurus and Rebbachisaurus, than why didn't
Carcharodontosaurus evolved one on it's back? This is troubling me for a
while and there seems to be no reason that could point into the right
direction...


>As for spinosaurs, as I mentioned above, its size would have given it the
same food requirements as a "warm-blooded" animal of the same size (how long
it could go without food is another story entirely though) and regardless of
physiology, an animal that big is going to have a large food supply no
matter what.
>
The Anaconda isn't a creature that is known for it's small size, the largest
one recorded was about 12 metres, coming close to a adult Spinosaurus. It's
is known that these creatures can live for several months on the remains of
their last lunch, a large crocodile or something like that.