[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: warm-blooded



In a message dated 97-07-11 13:00:27 EDT, mshelly@noclant.navy.mil writes:

<< Re: Warm-blooded
 On Thu, 10 Jul 1997  Dinogeorge writes:
>Did you >directly< measure their body temperatures? That's the ONLY
acceptable >evidence.>>

<<    We can not take the pulse of a dinosaur either but we believe they
lived. A jury can send a man to death but it never actually sees the crime.
 What we believe is fact is based on the preponderance of the evidence and is
only as good as the evidence.>>

Your analogy is inapt, because juries have sent people to the gallows
wrongly. And acquitted criminals wrongly.

Believing something is a fact does >not< constitute proof. You can believe
dinosaurs were endothermic, ectothermic, or something in between, and you can
give your reasons for your beliefs, but such reasons are only hypotheses. You
cannot exclude the (quite likely, in my opinion) possibility that dinosaurs
were metabolically different from (fully endothermic and fully ectothermic)
living forms unless you actually take their temperatures over a period of
time and chart them. Good luck with the latter.

<<    The only facts in paleontology are what was found and where.  The rest
is just theories trying to make the best fit with the information we know at
 the time.  The question is which theories fit the evidence better.
Therefore, I usually get upset when someone says that the only possibility
for ... was... I prefer someone saying ?Many paleontologists...?  or  ?My
 theory is ....?.>>

This is fine. A tautology, actually: a hypothesis is a hypothesis is a
hypothesis.

<<    A better question than were dinosaurs endothermic or warm-blooded is
?Were the dinosaurs energetic like modern birds and mammals?. I think the
evidence supports active energetic dinosaurs.  Dinosaurs apparently dominated
the landscape over energetic mammals for over 150 million years.  Some
appeared to live in vast herds, presumably moving over large areas.  Some
appeared to grow quite rapidly.   Others achieved large sizes.  Some even
descended into birds.

   The facts show that at least twice, endothermy developed in diverse
animals. Why did dinosaurs surpass other similar bipedal thecodonts, leaving
only the crocodillians in the cold-blooded predator niches?  How did
pterosaurs get the energy to develop flight?  When did the bird lung and four
chamber heart allow the development of endothermy?  One explanation that
could combine all these thoughts is that endothermy developed in the
bird/dinosaur/pterosaur ancestors and allowed active lifestyles to develop.>>

Maybe you're right. And maybe you're wrong. And: there almost certainly
weren't any obligatorily bipedal thecodontians. All material of such supposed
bipedal pre-dinosaurian archosaurs is either (1) too fragmentary for a
definitive statement; (2) composite, e.g., confusing juvenile with adult
remains or small animals with large; or (3) primitive dinosaurian (e.g.,
lagosuchians). This seems to be one of those dinosaurological myths that has
come down to us from the early days of dinosaurology. This is not to say that
many small quadrupedal thecodontians couldn't run bipedally if they had to,
like modern quadrupedal lizards do; just that they didn't do this habitually,
and certainly they didn't do this because their forelimbs were so small that
they were obliged to (like _Tyrannosaurus rex_).

<<    In summary, you could say that many paleontologist believe that some or
all dinosaurs had metabolisms and activity levels similar to birds and
mammals. However, not everyone is in agreement, especially on how, when, or
where endothermy developed.>>

Even if everyone were in agreement, everyone could be wrong.

<< >Everything< else is supposition, >hypothesis, speculation.
    That is the fun part of paleontology, speculating about how the dinosaurs
or other animals lived and how they might have evolved, then seeing if the
evidence shoots  you down or not.>>

Heh, heh. Sorry for raining a bit on your parade.