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



Here is Mr. T. Jones' response to my message.

V.
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>Terry D. Jones wrote:
>> If an animal has high metabolism (high O2 consumption)
>> and therefore high lung ventilation rates, the nasal passage 
>> proper must be large enough to accomodate increased 
>> airflow. In order to house the RTs (which as has been pointed out 
>> many times, >99% of endotherms possess), without increasing
>> resistance to airflow, the nasal passage of endotherms must be 
>> larger still.   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.

No, erect posture is not required for endothermy, whereas increased O2
consumption and lung ventilation and hence larger diameter nasal passages
are.

>> 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--these 
>> two terms are not synonoumous-- it is possible to have a large, 
>> insignificant data set if the methhodology is not sound), 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).
 
There is no jump from Poiseuille to nasal passage size.  This law
deals with movement of fluid in a tube, the nasal passage is tube in
which fluid (air) moves.

The olfactory appartus (in endotherms and ectotherms) is located in a blind
"cul de sac" out of the path of air flow (dorsal and posterior to the nasal
passage proper) where a sample of the air can be taken.  You don't want to
sample all the air, this would overload the system.

In general, endotherms are mouth breathers only during periods of intense
exercise.  Mouth breathing enables them to by-pass the RTs and dump heat as
well as increasing air intake--at the expense of resp. water loss.

As far as sampling size, I would encourage anyone to follow our
methodology, look at as many specimens as they want, you'll find the
same thing.  You don't even have to be this technical, just look and
endotherm and ectotherm of the same mass--you'll see that the
endotherm always has a large nasal passage.

>> 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.
 
No--RTs ARE causally and functionally linked to endothermy unlike
erect limb posture, etc.  W. J. Hillenius has already shown that if
you bypass the RTs in a mammal, the amount of respiratory water loss
would through the daily water flux out of balance.  Current work in
our lab show the same for birds.

>> 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.
 
No--crocs have a metabolic rate indistinguishable from other ectotherms and
no higher activity level.  

> 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.  

Most crocodilians primarily eat ecotherms (e.g., fish).  They will eat
just about anything they can get a hold of however.  None are
particularly specilaized to eating endotherms.  Moreover, there are
MANY endotherms that can stay submerged from much longer than a croc
(most marine mammals).  Also, some turtles can stay submerged from
months.

>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.  
 
Not true, they do keep constant body temp.
 
> 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).
 
As I pointed out, there are endothems and ectotherms that have sprawling
limb posture, and endotherms and ectotherms that have erect limb posture.
Therefore posture is not correlated with metabolism.

>> 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.

The problem wasn't time--the specimens aren't there.  A good three
dimensionally preserved dinosaur skull is a rare find....Because there
were so few dinosaurs head in existence, we could not and did not
conclude that all dinosaurs were ectotherms.  Given what is currently
understood about the relationships of the dinosaurs we looked at we
could say that based on our evidence, a variety of Cretaceous
theropods, and at least on genus of ornithischian didn't have room to
accommodate RTs.  From this we can deduce that at least these were not
endothermic.

>> 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.

Once again, there is NO direct evidence of endothermy in dinosaurs!!!  None
of the arguments generally given for endothermy in dinosaurs is causually
linked to endothermy--in most cases even the indirect relationship is
equivocal.  A plethora of circumstantial evidence  does not contradict one
piece of direct evidence--but one piece of direct evidence does contractict
a plethora of circumstantial evidence.  

There is an easy way to decide for yourself...

List all features of modern birds and mammals that are directly linked
(i.e., functionally and causally linked) to endothermy (therefore this
list could not include: ilium length, posture, etc).  This list may
include: insulation (not just flight feathers, but real insulation),
four-chambered heart (not functionally four-chambered as in crocs),
high respiratory surface area: lung vol., high resting rates of O2
consumption, high lung ventilation rates, (if I were doing it, as we
did when we started looking at this question long ago, I would include
RTs and large nasal passage diameter)...You decide what should be
included (just be sure that they are causally linked to endothermy--
required for endothermy).  Do the same for ectothermy.  Once the list
is complete see which of these there is evidence for in dinosaurs.  I
am confident that none of the things in your endotherm list will you
be able to find evidence for in dinosaurs.

Feel free to send this on to the dino list, if you like.  However, this is
my last message on the subject until something new comes along.

>Van Smith
>vksmith@dwx.com
>----------
>Watch _Babylon 5_. 

TDJ
:-{)
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    Terry D. Jones                             Voice:  541/737-6120       |
    Oregon State University              Fax:      541/737-0501          
    Dept. of Zoology                         JONEST@bcc.orst.edu
    3029 Cordley Hall
    Corvallis, OR  97331-2914
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