Q: "It's possible I'm misunderstanding this description of the dentition,
but if 16/18 means 16 teeth upper and 18 lower, shouldn't it be 34? Just
proving I'm still paying attention."
 
A: I just HATE those optical engineering types that know how to count!
 
Hey, who said I could add?  That was sum number, eh?  That's why I use
electronic calipers to dump the stuff directly into my beautiful, fast,
smart Macintosh G-3 laptop!  I must have made the mistake working with a
pentium on a PC.  Really.  Honest.
 
Ok, its my fault; it was a dumb typo I should have caught.  What was really
dumb about it was I remember looking at it and thinking that I never
realized ferrets had the same number of teeth as humans before.  And I
*KNEW* ferrets had 34 teeth.  Been counting them for years.  Oooooops,
brain fart in front of America.  <blush>
 
Here is the corrected dental formula:
 
i 3/3, c 1/1, p 3/3, m 1/2 = 16/18 = 34.
 
The dental formula is not the same thing as a dentist's formula for fixing
teeth (in that scheme, each tooth has it's own number).  In the zoologist's
dental formula scheme, the mouth is divided into four sections: upper and
lower, and right and left.  Since the teeth in the mouth are symetrical,
the right side matches the left, so there is no reason to write things down
twice, which is why 3-1-3-1 = 16.  3-1-3-1 represents the teeth in a single
qudrant, but 16 represents the number of teeth in the upper (or lower) jaw.
3/3 represents 3 upper and 3 lower teeth.  3/3-1/1-3/3-1/2 represents 3
upper and lower incisors, 1 upper and lower canine, 3 upper and lower
premolars, and 1 upper and 2 lower molars in the right (or left) half of
the jaw.  16/18 = 34 represents 16 upper teeth and 18 lower teeth for a
total of 34 teeth in the upper and lower jaws.  Sometimes, especially in
older books, the formula might be represented as:
 
i = 3-3/3-3, c = 1-1/1-1, pm = 3-3/3-3, m = 1-1/2-2 = 34.
 
It is also often seen as:
 
3-1-3-1/3-1-3-2 = 34, or as:
 
3-1-3-1
_______ = 34.
3-1-3-2
 
The teeth are always listed in order of appearence in the jaw;
incisors-canines-premolars-molars, or i-c-p-m.  If the formula represents
baby teeth, then it would be di-dc-dp-dm, or deciduous incisors, etc.  It
is always assumed the dental formula is representing adult dentition unless
it has the "d" in front of it, such as d3/3-1/1-3/3-0/0.
 
Incisors are the tiny little teeth between the eye teeth.  Their function
in carnivores includes holding stuff, grooming, nibbling, flea and tick
killing, and pulling out hair.  The canines, or eye-teeth, are used to kill
prey and for defense.  The premolars in ferrets are used for cutting and
tearing, and the tiny little molars are used to crush food.  They are very
tiny in the ferret because it is a primary carnivore and eats little food
requiring chewing.  Ferrets typically cut their food into small enough
chunks to swallow whole.  (Kibble is cut the same way, but the hardness of
the food grinds down the cutting teeth at a much faster rate than normal).
 
Sorry for the typo, or rather, my braino.  And THANKS to my great friend
for pointing it out to me!  Really.  Honest.  ;-)
 
Bob C and 20 MO Brainfartin' Buffoons
[Posted in FML issue 2359]