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Re: _Discover_ article



In a message dated 96-11-25 13:39:14 EST, longrich@stardot.com (Nick
Longrich) writes:

> Finally, a full-body insulatory coat on the theropod Sinosauropteryx 
> is very good evidence that it was fully endothermic (endothermy 
> naturally being a diverse range of physiologies encompassing extremes 
> such as the lukewarm monotremes and the hot-blooded songbirds) and it is 
> simplest just to assume that this animal was warm-blooded. This, and the 
> fact that close dinosaurian relatives, the pterosaurs also appear to have 
> had insulation, further supports the possibility that dinosaurs as a 
> group may have been endotherms. 

Perhaps we should imagine dinosaurs as endotherms that had not yet evolved
the kinds of nasal turbinates seen in extant birds. The very wide antorbital
fenestrae of most theropods and many sauropodomorphs, with accompanying
invasive pneumatization of the neighboring skull bones, may have supported
soft-tissue structures that served the same purpose. Once the turbinates
appeared in birds, that particular respiratory function of the antorbital
fenestrae was no longer needed, so the fenestrae diminished and ultimately
vanished.