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round II



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>
  To: rowe@lepomis.psych.upenn.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
  text]).
  
  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
  literature.
  
  As usual, feel free to distribute this -- Talk to you later John R.