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My, life sure is getting exciting around here isn't it. I've got the
next installation from John Ruben:
Date: Thu, 14 Sep 1995 12:10:07 -0700 (PDT)
From: John Ruben <rubenj@BCC.ORST.EDU>
Subject: re paul (again)
Mickey - thanks for forwarding Paul's communications. It is
important for your readers to keep in mind that, Paul's statements
notwithstanding, virtually ALL endotherms (>99%) have functional
respiratory turbinates (RTs), while they are ALWAYS absent in all
ectotherms. Moreover, Paul's contributions to the subject of RTs
should be regarded with caution--they contain extensive inaccuracies
and distortions (e.g., elephants, sirenians, and even whales do NOT
lack maxilloturbinates. For example, re elephants, check the table
on p.142 of the very source cited by Paul! [Negus' 1958 comp anat
Turbinates ARE poorly developed in whales due, no doubt, to the
immense specialization their nasal passage has undergone.
Nevertheless cetaceans exhibit some little known, but nevertheless
fascinating specializations to compensate for the probable loss of
much of the original function of their respiratory turbinates and
the need for respiratory water retention in endotherms (see for
example Coulombe et al., 1965, SCIENCE, 149:86-88).
It is also misleading to assume that even relatively simple
respiratory turbinates lack an important respiratory water retention
function. For example, humans have about as simple a series of RTs
as you're likely to find in any tetrapod, yet they are good enough
to reduce respiratory water loss by about 50%(!).
Turbinates AND nostrils ARE absent in some pelecaniform birds-- but
all are specialized divers and it is generally thought that open
nostrils would be a liability in such cases. Nevertheless, all have
well-developed salt glands that enable them to drink quantities of
sea water sufficient to compensate for increased rates of
respiratory water loss.
The extremely rare exceptions noted above where RTs are absent in
endotherms are clearly secondary and related to other requirements
that preclude their presence. Moreover, in virtually all of these
exceptions, the companion presence of other distinct specializations
to compensate for the absence of RTs would seem to reinforce the
notion that endothermic metabolic rates necessitate some mechanism
to reduce respiratory water loss. RTs (which, again, are NEVER
present in ANY extant ectotherm) clearly evolved independently in
birds and mammals --thus, without exception, the evolution of
respiratory turbinates seem to have been the ancestral solution to
high rates of respiratory water loss in early birds and
mammals. Their apparent total absence in all dinosaurs would seem to
be a strong indication that most, if not all, members of the group
lacked high rates of lung ventilation (and respiratory water loss)
associated with endothermy.
Finally, it is highly disingenious of Paul to assert that the water
retention capacity of RTs is not generally accepted. Such a
statement would certainly come as a surprise to the likes of Knut
Schmidt-Neilsen, since he was among the first comparative
physiologists to study the respiratory water (and heat) retention
capacity afforded by the presence of RTs in mammals and
birds. Hillenius' contribution has been to add to the data base and
to point out the evolutionary importance of RTs. He's never claimed
to have been the first to describe their role in reducing
respiratory water loss.
As for the rest of Paul's missive(s), the errors and inaccuracies
are so extensive that I just don't have time to deal with them now.
Again, for an objective review of the topic of dinosaur metabolic
rate, I urge your readers to see Farlow et al. DINOSAUR BIOLOGY
(1995, Ann Rev of Ecology & Systematics, 26:445-471). Reviews
appearing in the Annual Review series are generally regarded as
among the most objective and authorative in the scientific
As usual, feel free to distribute this -- Talk to you later John R.