Re: Dinosaurs Were Endotherms (long)

["Matthew Troutman" <m_troutman@hotmail.com>]

>> Still, there does not 
>> seem enough room for there to be a posterior region in dinosaurs.
>
>We disagree.

     The constricted and laterally compressed _preorbital_ ( meaning all 
the space ahead of the orbit ) could not house of turbinate. 

> Look 
>> closely at the Ornithomimus skull in _ The Complete Dinosaur _, the 
>> whole entire pre-antorbital cavity region in Ornithomimus is narrow,
>
>...as is the anterior nasal passage of the kiwi...

     The kiwi is a very derived bird. It is the only bird that has 
nostrils at the tip of its bill and it has a very derived, elongate beak 
that is used for probing. The kiwi is very abberant among birds and I do 
not think it is good to compare a specialized bird to a dinosaur where 
not all the same features are held true. 


<<Yes, the snout could be described as "narrow," but I still see a 
vacant space which could have housed the middle respiratory turbinate. 
>>

     Turbinates are not held in the small spaces of the nasal passage, 
the functional turbinates are in the posterior nasal cavity, which is 
very large.


<<In my opinion, the respiratory turbinate papers make a strong argument 
against endothermy in non-avian dinosaurs until you take a closer look 
at the actual data (versus the interpretation and presentation of the 
data), and at this point you must decide for yourself whether the 
authors have truly taken an even-handed approach to the subject and 
whether theirs is such an open-and-shut case.>>

    I have talked to Jones off list and their approach was as even 
handed as possible. There are no big variations in the measure of the 
nasal passage in dinosaurs.

<< Advocates of ectothermy in all non-avian dinosaurs will not succeed 
in convincing me until they can explain the metabolic mandate for an 
insulating pelage on small ectothermic theropods.>>

     That is a rather irrelevant problem. There are many birds that need 
to bask in the sun to be able to raise their body temperature ( turkey 
vultures, roadrunners, woodhoopoes ). They have a complete insulatory 
pelage and they have to bask in the sun to raise their body temperature. 
Now, coraciiform birds have to nest in tree trunks so they have to be 
sheltered from the colder winter air, and they are fully insulated. The 
"feather" problem is actually not that much of a problem.


MattTroutman

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