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Re: Warm- vs. Cold-blooded Dinos



I am going to plunge in head first with what I have learned, please feel
free to correct any errors I'm not touchy ; )

>1. Upright Gait: Almost all dinosaurs had long, limber, upright limbs held
>underneath the body like most modern endotherms.  This gait implies
>high levels of activity and are unlike sluggish ectotherms like lizards and
>crocodiles whose limbs are sprawling or semi-sprawling at best.

        This is also important when you consider Carrier(sp?) constraint
which is when the side to side swing of the reptiles gait interfears with
the lungs and they cannot travel long distances at high rates of speed
without having to stop to breath, watch a lizard run for awhile, it will
stop at certain intervals. This is to catch it's breath.

>2. Predator-Prey ratios: Endothermic animals need much more to eat ...

        I had recently mentioned to Steven on an aside posting that I was
pretty sure that the scientific community had some serious doubts about the
validity of many of our older notions of predator/prey ratios. Anybody else?
or was it just me?

>5. Growth Rings: Animals with low, ectothermic metabolism grow slowly 
>and leave marks of their slow growth in rings in bone cross-sections,
>almost like rings in a tree trunk.  High-metabolism endotherms like 
>mammals grow quickly and build up their bone tissues much faster and
>more homogeneously, resulting in a lack of "growth rings" in their bone
>cross sections.  Examinations of dinosaur bones reveal a lack of "growth
>rings," implying fast growth, and a high endothermic metabolism.

        Wasen't there recently some new work done on this which showed
growth rings in dinosaurs thought to be endothermic? Again, it's just a hint
of a memory. I think it was a woman doing the research.

        Lastly, I belive that many of the smaller dinosaurs especially the
little carnivors were endothermic. I would like it if someone out there
could clarify for us the difference. Aren't there several terms involved
here involving metabolism, I seem to remember there were several different
states not just warm vs cold. You could be warm blooded but not able to
maintain it and some critters that are considered ectothermic can actually
control their temperature for certain body areas. It's all very confusing so
I hope one of you Profs can sort all of this rambling out and post a guide
line for the different states of  "bloodedness". And in conclusion one other
question, isn't there a formula where at a certain mass warm bloodedness
becomes a problem and you get enough energy from your surrounding that you
don't need to invest metabolically in temperature control?
                                
                                Sorry this is so long ; )       Jennifer FWP