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Re: dinosaur anatomy



In a message dated 97-12-08 03:10:05 EST, you write:

<< >From _Discover_ magazine, December 1996, _A Cold, Hard Look at Dinosaurs_,
 by Virginia Morell, page 107:
 
 "When Hillenius looked at birds, he found evidence of turbinates only as
 far back as 70 million years -- a little under half the time since they
 originated from dinosaurs.  And when he finally looked at dinosaurs
 themselves, he found none -- which meant, he concluded, that the dinosaurs
 were not warm-blooded."  >>

 Hi, thank you. I'm finally replying. I'm a college sophomore, and this is a
busy time in the semester. I'm not a science writer, just a prehistory
enthusiast. But I did some reading and research for this reply.

 I was hoping someone would mention that quote from Discover. I found it
puzzling that it did not mention Archaeopteryx by name. Lack of  nasal
turbinates in Archaeopteryx, or in other birds earlier that the "70 million
years,"  by itself could mean one of two things:

1) Nasal turbinates were not necessary for those birds, thus keeping them
endothermic. (In Science, vol. 273 p.1207, Ruben et al states that diving
birds of the order Pelecaniformes lack both turbinates and nostrils. These
[endothermic] birds do not need them because of their lifestyle. The same is
true for other rare exceptions.)
2) Nasal turbinates are necessary for endothermy and those beasts were
ectothermic.

 I especially liked Ruben's recent article in Science vol. 278 p. 1267. There
it was stated directly that early birds and Archaeopteryx were ectothermic. I
found this very surprising. To me it only seems logical that a beast with some
form of insulation would be naturally endothermic. Could it be that feathers
had the primary use of flight and the secondary use of insulation for those
birds? If so, that seems to indicate something about the environment of that
time. The Jurassic environment was hot and tropical, right? So maybe
endothermic metabolisms were not needed for those birds (and dinosaurs by
extension).

 When studying dinosaurs, I find that they do not easily fit into either of
the endothermic or ectothermic molds. It looks like Archaeopteryx may not
either.

 Thank you.
 Have a nice day.