[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Dinosaur Were Endotherms (sic)
<<I know that I confused the RT issue by erroneously stating that
someone had written that kiwis had no respiratory turbinates. I was
wrong; they havethem, despite their small tube-shaped nasal passages,
which shows (asGregory S. Paul has pointed out) that RT's can be present
without the nasals being especially capacious in the region of the RT's.
This is telling, because it means that the kiwi skull would fail the
Ruben/Jones/Geist/Hillenius test for RT's, and hence, this known
endotherm would be judged an ectotherm. (The RT team conceded that
pelicans had no
>RT's, but their semi-aquatic habits were taken to be the reason these
>didn't dehydrate). >>
I believe GSP was just refering to the anterior nasal passage in
the kiwi. He stated that Ruben et al. did measure this in their papers
on turbinates but did not measure the posterior nasal cavity, which can
hold turbinates. This is incorrect because in the figures in the Ruben
et al. Science paper and the Complete Dinosaur show the entire nasal
passage highlighted. If there was a posterior nasal cavity, it would be
very short because the internal nares are almost always opposite the
antorbital cavity in dinosaurs. This would preclude RTs.
>>Furthermore, when the above-named team quantified the nasal passage
cross-sections of fossilized dinosaur crania to compare with the
cross-sections of the respiratory turbinate regions of extant endotherms
and ectotherms, they apparently performed their sections anterior to
where the RT would most likely be found in life, for the probable site
of the RT in a dinosaur skull is (correct me if I'm wrong) in the middle
of an empty cavity farther aft which gives no indication of the
dimensions of nasal
passages. As Luis Rey suggests, dinosaurs may have had RT's which
weren't ossified. The illustration of the air flow through the nasal
passage of a dromaeosaur skull in the RT article in _The Complete
has come under fire as inaccurate, based on an out-of-date
The position is verible, but the whole passage was narrow according
to the figures in the papers. See above.
The dromaeosaur skull in _ The Complete Dinosaur _ was one figured by
Currie in 1995, hardly old. It may well be inaccurate, though.
Boy, I can feel the flaming getting closer.
Get Your Private, Free Email at http://www.hotmail.com