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Re: choana [was SOME SVP TIDBITS]



Some clarification, please, for us non-anatomists:

Tom Holtz said (10/9/98; 9:41a):


>>Perhaps someone could say what a choana is too?<<

>Sorry, let that one slip out. Internal nostril (the opening inside the 
roof
of the mouth at the other end of the nasal passage).  In mammals and our
ancestors, birds, and modern crocs it is far back in the throat; in most
other reptiles (including non-maniraptoriform, and non-spinosaurid,
theropods) it opens closer to the front of the mouth.<


First:  I always use the term internal naris for the opening through 
bone, and thought "nostril" implies inclusion of associated soft tissues 
(analogous to orbit vs. eye socket).

Second:  Is "choana" really synonymous with "internal naris", or does it 
refer to the opening where inhaled air passes freely into the opening of 
the mouth cavity or throat (implied above).  In other words, for animals 
that have a secondary palate, is the choana farther back than the 
internal naris?  This implies to me that choana and internal naris are 
different.  Might internal naris still be the proper term for the more 
anterior opening, but one that opens into a passage between the primary 
and secondary palate (leading ultimately to a more posterior opening 
where the air hits the freer space of mouth cavity and/or throat, that 
perhaps has a different name???)?

Thanks, in advance.

*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
Norman R. King                                       tel:  (812) 464-1794
Department of Geosciences                            fax:  (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712                      e-mail:  nking.ucs@smtp.usi.edu