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Re: [GSP1954@aol.com: MORE DINOSAUR ENERGETICS]



Here is a message that I sent this list and Mr. T. Jones. Mr. Rowe
suggested I clean up the formatting (it looked messy after I sent it) 
and clip some of the quoted material.

T. Jones replied and gave permission to send his reply to 
the list so I'll forward that as well.

V.
__________

Terry D. Jones wrote:

> If an animal has high metabolism (high O2 consumption)...
> ... For the same reason ectotherms have narrower nasal 
> passages since they have lower metabolism and 
> correspondingly low lung ventilation rates. 

Conjecture bearing no more or less weight than erect limb posture, etc.

> This is not a result of our work, but it is a law of physics
> (Poiseuille's law:  flow rate is proportional to radius^4  -- 
> in other words,  decreasing the radius of a tube by 1/2 
> increases the resistance to flow 16x).

No one is debating physics (see below).

> Regardless of how many specimens you observe 
> (our data set may not have been large, but they were 
> significant... ...this law still governs the size of the 
> nasal passage--you can't have an endotherm with
> a narrow nasal passage (relative to body mass).

This seems like a very hasty conclusion to jump from 
Poiseuille's Law to nostril sizes of endotherms vs. 
ectotherms.  Perhaps some endotherms were mouth
breathers.  Perhaps the fact that, as a rule, mammals have
highly developed olfactory equipment, the larger nostril size
was developed in many of them to enhance this sense.  The 
crux of Mr. Paul's problem with your study seems to lie in your
sampling size (this is certainly my biggest problem with your
arguments).

> It may appear that some endotherms have relativeley 
> narrow air passages (or that some ectotherms have large air 
> passages), but when compared with body mass, the 
> relationship holds true--there is an approximately 4-fold 
> gap between the nasal x.s. area of modern endo- and 
> ectotherms when compared to body mass.  I'm waiting 
> eagerly for the results of Greg's work to  come out in
> print...I hope there is an explanation included for the
> apparent contradiction of Poiseuille's law.

I reread Mr. Paul's message and I find it difficult to see
how your remarks are relevant at all.  Mr. Paul had a 
problem, and I think a well founded problem, with you 
sample size.  Your dismissive and evasive arguments are
not persuasive.

> As I said before, the features (e.g., erect limb posture)
> presented by Greg as "evidence" of endothermy in 
> dinosaurs are not causally or functionally linked to 
> metabolic rate.  There are and have been animals with 
> erect limb posture that aren't or weren't (as far as we know) 
> endotherms. 

Analogous arguments can be made against your proposition.

> Also, crocodilians have semi-erect limb posture 
> but their metabolic rate is the same as other modern 
> ectotherms.  If posture is causally linked to metabolism
> you would expect crocs to have "intermediate" metabolic
> rates.

This argument does little to further your case since crocodilians 
possess perhaps the most advanced and efficient heart of all 
ectotherms.  Their heart enables a higher level of activity than
is normal for ectotherms.  Due to their lifestyle -- drowning their 
endothermic prey -- it benefits them to have a lower metabolism 
than their large, endothermic prey since it enables them to stay 
underwater for much longer periods of time than their prey.  

Crocodilians were either on their way to becoming warm blooded,
or are perhaps even secondarily ectothermic.

> Moreover,  some mammals don't have erect limb posture
> but are still endotherms. 

The only mammals that come to mind are monotremes and they
do not maintain a constant body temperature.  But even if there 
are many other examples, the converse of a true statement is 
often false.  Your statement is completely irrelevant to the Mr. 
Paul's argument: erect limb posture is a piece of evidence that 
suggests dinosaurs might have been endothermic (and with 
high metabolisms).
 
> By the way, the three dinosaurs we used were the only
>  three available. There was no horned dinosaurs that are 
> preserved 3-dimensionally and not significantly altered by
> preparation.  Maybe Greg has access to specimens we
> don't know of...

If I only had time to survey three people for a presidential 
election, my poll would probably not be very accurate, 
either.

> Recently a student asked me "why is it so important
> to some people to have dinosaurs be 'warm-blooded'?"
> I couldn't answer the question, maybe someone
> can help...

More evidence than not suggests that dinosaurs were
warm-blooded.

Van Smith
vksmith@dwx.com
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