respiratory turbinates

[nking.ucs@smtp.usi.edu]

[Thanks, Norm.  Due to some (now solved) problems last week, Achut's
 message appeared to have come from me.  As a result, two people
 responded to me personally to tell me about the Ruben _et al._
 article (which I'd already read, but thanks!).  Due to another screw
 up on my part, I lost the address of one of you yesterday.  In any
 event, I'm glad to see this information go out to the list with
 little work on my part! :-)  -- MR ]

On Wed, 4 Sep 1996 16:07:37, Achut Reddy wrote:

>I saw an article in the local paper that
>someone had done a study by CAT-scanning the noses
>of various well-preserved specimens of a broad range
>of dinosaurs.  They apparently found that the nose
>structures were very reptile-like, and based on this,
>made the jump to the conclusion that all dinos must be
>cold-blooded.

>Does anyone have more details on this study?

This information may be from an article published in Science (v. 273, 30 
August, 1996, p. 1204-1207), by J. A. Ruben, W. J. Hillenius, N. R. 
Geist, A. Leitch, T. D. Jones, P. J. Curie, J. R. Horner, and G. Espe 
III, entitled The Metabolic Status of Some Late Cretaceous Dinosaurs.

They examined the nasal regions of Nanotyrannus, Ornithomimus, 
Dromaeosaurus, and Hypacrosaurus, looking for evidence of, or room for, 
respiratory turbinates, as are found in more than 99% of living birds and 
mammals.  They concluded that the dinosaurs examined did not have room 
for such structures--the nasal passages were too constricted, and the 
external nostrils were too close to the internal nostrils in the roof of 
the mouth.  In these dinosaurs, the nasal region was more similar to that 
of crocodilians and lizards.

The authors suggested that presence or absence of respiratory turbinates 
may be used to assess the metabolic status of extinct vertebrates.  
Respiratory turbinates and otherwise enlarged nasal passages are believed 
to be associated with elevated lung ventilation rates, and, by extension, 
with high routine metabolic rates.  Their absence implies that metabolic 
and lung ventilation rates were sufficiently low that evaporative water 
and heat loss was not a problem.

They concluded their paper with the following statement: "These 
observations do not necessarily either preclude or support the 
possibility that some or all of the taxa investigated here maintained 
routine metabolic rates somewhat greater than those of extant 
ectotherms."

So, they didn't quite jump to the conclusion you suggested.  However, 
they did seem to conclude that the taxa investigated were not likely "as 
endothermic" as living birds and mammals.


*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
Norman R. King                                       tel:  (812) 464-1794
Department of Geosciences                            fax:  (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712                      e-mail:  nking.ucs@smtp.usi.edu