RE: Regarding Spinosaurus

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

Fam Jansma wrote:

>The sail on the back of Spinosaurus could be clue to the coolbloodiness
>of this critter. 

It's very possible, but I'd be hesitant at drawing this conclusion.  Even
mammals and birds make use of additional strategies to warm themselves up
beyond what their endothermic metabolism can provide.  It certainly "saves"
the amount of fuel a mammal or bird has to burn if it can make use of
exogenous heat.  (I'm thinking of elephant ears and vulture heads when
writing this, but there are plenty of other examples I'm sure.)

For endotherms wanting to rid themselves of excess heat, there are
strategies for this too.  Like sweating or panting (in mammals), or coating
your legs in urea (in birds), or just finding a shady spot.  

For both reasons (heat loss and heat gain), a sail in a predominantly
homeothermic animal (which I think dinosaurs were), especially one living in
a climate of temperature extremes from night, might make a lot of sense.

>Look at present reptiles, they need to warm themselves in the morning >to
"activate" themselves in the morning

One mammal (me) needs a hot cup of tea or coffee for that. 



Tim

and because of their
colbloodiness, they need less food. A sail would surely have speeded up
the
process so the Spinosaurus was able to hunt 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 big
fish-supply.

>Nick P.


Rutger Jansma