Dear Deb and others,

Unless somebody has a specific question for me I'll bow out of this 
debate, after two comments and one question.

When Huxley defined human m1 and m2 as deciduous he was doing so in a 
technical manual "Lessons in Elementary Physiology". He was not, as Deb 
surmises, engaging in popular rhetoric as Darwin's bulldog. What he says 
is not found just in quaint, old-fashioned literature. I am looking at 
Berkovitz et al (1992) "A Colour Atlas & Textbook of Oral Anatomy" and 
reading the phrase 'Mandibular second deciduous molar'.

Good luck to anybody who tries to standardise the terminology across the 
two systems of evolutionary and descriptive human anatomy. I think you 
would produce a poorer outcome than the creators of the Euro.

Deb - you mention the  International Commmission on Zoological 
Nomenclature as dealing with the nomenclature of premolar, molar and 
deciduous teeth. I thought they dealt with the scientific names of 
animals, not with anatomy. I have looked at the contents of their "Code" at

http://www.nhm.ac.uk/hosted-sites/iczn/code/

and can't see any chapter that looks relevant. Am I missing something?

Richard


Anyway,
On 9/10/2012 18:47, [log in to unmask] wrote:
> Richard, and all: Yes, the noble kangaroo is liable to be offended with
> me, albeit his dentition is in truth the object of another convention. In
> other words, what Richard says about kangaroos (and other marsupials,
> including Didelphis) having 4 molars is correct according to the current
> and accepted convention, and in saying otherwise I was in error: what I
> should have said was that 'no PLACENTAL mammal has more than 3 molars' --
> unless, of course, we listen to people who work on Cetacea, who will
> remind us that they can't tell how many molars a toothed whale might have,
> thanks to their acquired monophyodonty.
>
> All of this, and Richard's question about our use of the term 'deciduous'
> for teeth which erupt from alveoli that contain two tooth-buds, must be
> answered from a knowledge of serial tooth-replacement. The diagram on p.
> 230 of Romer's "Vertebrate Body" is taken from a paper by Edmund, although
> unfortunately I can't find Edmund in the citations for that chapter
> (perhaps somebody here would know the exact reference). Understanding Fig.
> 222 on p. 232, which shows the 'rolling' development, attrition, and
> shedding of teeth in the jaw of a shark, is crucial (ergo standard stuff
> on vert. paleo. and comparative anatomy exams).
>
> Romer then presents what is really the same diagram as Edmund's, modified
> (simplified) to apply only to mammals; see p. 236, Fig. 231. The caption
> says: "One complete set of teeth develops from incisors back to molars.
> All of these except the molars, however, are shed .... A second set of
> teeth then develops, but never produces molars. Hence the 'permanent'
> dentition includes portions of two tooth series" [i.e. Romer means the
> 'series' of Edmund].
>
> This is an important realization: the molar teeth, erupting as they do
> from alveoli containing but a single tooth-bud, are actually just
> late-erupting, posteriorly-located teeth belonging to the FIRST series,
> i.e. that which in the next more anterior part of the jaw, develops and
> erupts the elder tooth-bud in those alveoli which contain two tooth-buds
> (i.e. those teeth which we term premolars).
>
> This is all that can be said about it, I think. In my own library, I can
> go back as far as H.F. Osborn's 1907 "Evolution of Mammalian Teeth" or his
> 1912 "Craniometry of the Equidae," or his 1918 "Iconoclastic Type Revision
> of the North American Equidae", and find him using the term 'deciduous' to
> describe those teeth which are by definition called premolars, that is,
> those which develop from the elder tooth-bud in alveoli which contain two
> tooth-buds.
>
> I find the same understanding in W.K. Gregory of about the same date, and
> in William Diller Matthew's work, as well as in Cope, Marsh, and Scott
> already cited in the previous memo. There were disagreements between these
> American workers and the great British comparative anatomist Edwin S.
> Goodrich, but not about this matter: they all agree that those cheek-teeth
> or "grinders" which are replaced are called premolars, and those which are
> not replaced are called molars.
>
> In J.S. Kingsley's "Comparative Anatomy of Vertebrates" (1917, P.
> Blakiston's & Son, Philadelphia) we get the following helpful information
> on p. 226: "Most vertebrates have a succession of teeth (polyphyodont
> dentition) and the elasmobranchs show how this has come about [i.e. this
> is an allusion to that all-important shark jaw illustration reproduced in
> Romer]...."In the non-mammalian classes the number of such dentitions is
> indefinite (polyphyodont), but in the great majority of mammals there are
> two, the first or milk dentition and the second or permanent dentition
> (diphyodont condition)."
>
> The term "milk dentition" or "milk tooth" is an acceptable, although
> somewhat informal, synonym of "deciduous dentition" or "deciduous tooth".
> Kingsley also uses the very formal "lacteal dentition" = "milk dentition"
> = "deciduous teeth". On p. 229, Kingsley says "In mammals....four kinds of
> teeth are recognized. These are the incisors in the premaxillary bones,
> followed by a single canine at the anterior end of each maxillary bone....
> Behind the canines come the premolars (the bicuspids of the dentists)
> which have two roots and complicated crowns and appear in both milk and
> permanent dentitions. Lastly are the molars, like the premolars in form,
> with several roots, but appearing only in the permanent dentition."
>
> On p. 412, Kingsley presents an astonishing diagram, after Rose (umlaut
> over the 'o') showing the relationship of each human tooth to the
> dentition in the shark. This diagram is a modification and expansion of
> Edmund's. The reference is Rose, Entwicklung des Saugethierherzens (umlaut
> over the 'a'), Morph. Jahrb., 15, 1890. This implies that the term
> "deciduous" must go back rather far, probably at least mid-19th century
> (we have previously concluded the same from its use by Cope).
>
> If I had Goodrich better represented in my library -- I possess only Vol.
> I, Chapters 1-8, of his monumental treatise comparing the anatomy of
> vertebrates -- we would probably find the ultimate answer. Goodrich's huge
> opus takes us back to the first decade of the 19th century, and he cites
> everybody from Cuvier onward.
>
> Richard has cited Huxley and other very old sources. They are lovely and
> interesting, as George Stubbs' 18th-century engravings of dissected horses
> are, too; but we no longer use the terminology with which Stubbs labeled
> the anatomical parts. So, to cite Huxley for being old or 'first in the
> field' so to speak, won't do us any good, because his work antedates
> better and more perceptive work -- especially that by Goodrich -- that
> came later.
>
> There is, in addition, some reason to suspect that if Huxley referred to
> all cheek-teeth as "molars" he may just have been speaking informally in
> an attempt to use common rather than technical language -- as we know, he
> did a lot of public proselytizing as 'Darwin's Bulldog'. Yet Huxley's
> contemporary, V.O. Kovalevsky, the early student of horse evolution who
> named Hyracotherium, had a perfectly clear understanding of tooth
> development and replacement. It might also behoove us to go back and check
> Cuvier, because for all I know his understanding was correct, too; perhaps
> someone else can fill us in concerning that.
>
> Above and beyond all this, we should not forget the venerable
> International Commmission on Zoological Nomenclature, who review and set
> the standards for all anatomical terminology, including that pertaining to
> teeth; and their usage of the terms "premolar", "molar", and "deciduous"
> is the modern standard which I have been outlining. -- Dr. Deb
>
>

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