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Re: CRANIAL-CAUDAL vs ANTERO-POSTERIOR



In an extremely rare and minor technical error, Darren wrote:

(and a cranial caudal vertebra would have to be called an anterior
caudal vertebra in the 'old' system anyway).

My understanding is that, in the tail, one does not use the terms "cranial" and "caudal" -- one uses "proximal" and "distal" instead. Thus, there are no "cranial caudal vertebrae;" there are, however, "proximal caudal vertebrae." I cannot, however, at this moment, put my finger on the source of that, although as previously noted, Larry Witmer noted this point to this list (Oct. 16, '98).


Just for everyone's edification, "anterior" and "posterior" now have only an extremely limited usage in modern anatomy (and since fossil organisms are related to modern ones, there is no good reason to have different terms for each!). To wit, for birds (upon which much dinosaurian anatomy should be based, terminologically speaking), _Nomina Anatomica Avium_ states:

"Cranial and caudal are used throughout the [_NAA_], except that rostral replaces cranial within the head from the level of the occipital condyles. Superior and inferior are entirely avoided, but the prefixes supra- and infra- are retained for convenience and because of long usage, e.g., Nervus infraorbitalis. Anterior and posterior are used only in the eye and ear...but again the prefix post- has occasionally been used in terms which are well established, such as Ligamentum postorbitale...That some anatomists stronlgly prefer anterior and posterior as general alternatives to cranial and caudal is recognized, because these are time-honored terms in the literature of vertebrate morphology. However, these terms can be confused through their entirely different meaning in human anatomy, where they refer to ventral and dorsal. Anyone not convinced of this potential confusion should examine the anatomical writings of the eminent nineteenth century prosectors of the Zoological Society of London...Although writing as zoologists in zoological journals, these authors commonly used anterior and posterior in the human sense. Sometimes the usage of human anatomy and the zoological usage were both employed in the same paper...Even so, it is not realistic to expect the instant and universal adoption of cranial and caudal; nevertheless, it is hope that eventually this will be achieved."

_Nomina Anatomica Veterinaria_ is much more protracted in its discussion, but says this:

"Anterior, posterior, superior, inferior. These terms cannot be generally applied to quadrupeds because of the confusion arising from their meaning in human anatomy. The use of these terms is restricted to some structures of the head."

There will, of course, be resistance to learning and applying the new usage, particularly among those who have the "old" system ingrained in their thinking. The same can be said of those who have rallied against the phylogenetic systematic/cladistic terminology in lieu of the established, long-used Linnaean system, but in either case, all it takes is a bit of practice, and an understanding of the shortcomings of older systems that the newer systems attempt to alleviate, and they too will become second nature.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
Dept of Earth & Environmental Science
University of Pennsylvania
240 S 33rd St
Philadelphia PA  19104-6316
Phone: (215) 573-8373
Fax: (215) 898-0964
E-mail: jdharris@sas.upenn.edu
and     dinogami@hotmail.com
http://www.sas.upenn.edu/~jdharris

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