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Re: feathers, fibers, endothermy...



Ever in need of carefully rereading things I think I understand, I have
some questions about the _New Insights Into Metabolic Physiology of
Dinosaurs_ chapter (by John Ruben et al.) in Farlow and Brett-Surman's _The
Complete Dinosaur_.

I had (wrongly) assumed that Figure 35.7, the chart on the bottom of page
513 which charts nasal passage proper cross-sectional area against body
mass for certain extinct species as well as for extant ectotherms and
endotherms, was actually a comparison of the nasal passages in the middle
(respiratory) turbinate region.  But no, this is a graph of the "nasal
passage proper" cross-sectional area.  So, as Paul suggests, the kiwi would
not track as an endotherm on this graph.  Unfortunately, the graph labels
points for the extinct taxa only, and does not specify where various extant
animal taxa would appear on the graph.

Similarly, I had assumed that the cross-sectional, computed axial
tomography (CT scans) of the three extant animals' nasal passages versus
the three dinosaurs' nasal passages (Figure 35.6) represented scans for all
of the animals at the location (or expected location) of the middle
(respiratory) turbinate.  But the caption states only that the
cross-sections are of the "nasal passages;" it is not clear if the nasal
passages are depicted just anterior to the internal nares or not.  Do the
selected images depict the point where the dinosaur nasal passages are at
their most capacious (as the passages theoretically ought to be in the
turbinate regions) or at any other point in the nasal continuum?

Furthermore, I would like to know what theropod experts have to say about
Figure 35.9, the illustration which depicts "the likely path of air flow
through the nasal region into the oral cavity" for the extant monitor
lizard, _Varanus_, and the maniraptoran theropod dinosaur, _Dromaeosaurus_.
 Does the path depicted for _Dromaeosaurus_ look accurate, and if so, would
such an anatomy preclude the existence of respiratory turbinate features in
dromaeosaurid theropods?

I would appreciate your indulging me with answers.  I admit that I have a
lot to learn.

Ralph Miller III <gbabcock@best.com>

"You are a wise man, Van Helsing, for one who has not lived even a single
lifetime."