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Re: Regarding Spinosaurus
Fam Jansma wrote:
>The sail on the back of Spinosaurus could be clue to the >coolbloodiness of
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.
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.
>Look at present reptiles, they need to
>warm themselves in the morning to "activate" themselves in the mrning >and
>because of their colbloodiness, they need less food.
Well kinda. At small sizes a bradymetabolic ("cold-blooded" if I must) animal
needs less food than a tachymetabolic one, at larger sizes this disparity
decreases and eventually leads to little or no disparity at all (see Farlow et
al's papers in the book: A Cold Look at the Warm-Blooded Dinosaurs).
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.
On the flip side, most mammals and birds need to eat as much as they can as
often as they can in order to keep activated.
Sorry, I just hate the wording of these things at times.
>A sail would surely have speeded up the process so the Spinosaurus was able to
>fish in the morning. Fish are a little numb in the morning, making >them
>easier to catch and so supplying the Spino every morning with a >scaly
>breakfast. If the Spinosaurus was coldblooded, it also needed >less fish to
>eat every day, so it wouldn't have needed a bigfish->supply.
Fish are functionally (or is that environmentally?) homeothermic due to the
thermal consistency of water, which might explain why I've never seen a logey
(sp?) or "numb" fish in the morning or evening.
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
As a side note, I've always been partial to the idea that _Spinosaurus_ evolved
that large sail in order to mimic the _Ouranosaurus_ of the time and sneak in
close to them. It's the ultimate "wolf in sheep's clothing" scenario. It's also
the ultimate in speculation, but at least it makes for a neat artistic
scenario...well, as long as one is willing to extend the length of time for
either _Ouranosaurus_ or _Spinosaurus_.
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