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RE: Making Lip of It



Lip flexibility is not really relevant. It should behave much like in lizards 
_at least_, where the band of tissues along the lip's margin pull at the entire 
margin from any one point, much as an elastic band does on one's waist or sock. 
In snakes, flexibility of the lip tissues is so great that the presence of 
scales could only matter during _compression_ of the lip tissues together, 
while the same should generally be true in lizards where pushing _up_ on a lip 
can cause you to push _out_ on the lip to involve the scales on the face and 
jaw, moving much like a chain-link fence does.

Cheers,

  Jaime A. Headden
  The Bite Stuff (site v2)
  http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)


----------------------------------------
> Date: Fri, 23 Sep 2011 15:20:07 -0300
> Subject: Re: Making Lip of It
> From: augustoharo@gmail.com
> To: qi_leong@hotmail.com
> CC: dinosaur@usc.edu
>
> 2011/9/23 Jaime Headden <qi_leong@hotmail.com>:
> >
> > I wouldn't be so sure that characteristics such as large canines are _not_ 
> > the product of natural selection. Just because the animal is of 
> > domesticated stock, not all aspects of siamese breeding is controlled, and 
> > deviations (such as Rex hair pattern or the Scottish' fold) can enter into 
> > the gene pool without controls, and then become spread through the pool by 
> > selective breeding. The mutations in body form, color, etc., can develop 
> > and spread without controls in domestic cats due to uncontrollable 
> > breeding. Fanciers and professional breeders are not the only method by 
> > which the population booms, as my American shorthair/Siamese mix can attest.
>
>
> A clarification: in the case of the siamese cats, I do not know if it
> is a long teeth or a short lip what implies the patter of lip not
> covering canines. You are right that natural selection may still act
> among domestic animals, most easy to see in the case of severely
> disabling genes. In the case of teeth and lips in Siamese cats, and
> accepting the possibility of natural selection having something to do
> with this condition, I would re-state my opinion is that they cannot
> be example of a natural condition evolving by natural selection,
> because it may not have arisen by natural selection.
>
> That said, I am skeptical of the powers of natural selection in the
> generation of the physical features in the case of cats. I think
> natural selection may in any case be more powerful in the case of
> alley or feral cats than house cats. For reproduction of house cats is
> partially controlled by humans, which, if out of fashion like some
> kind of curly hair or ears, will selectively breed. It seems that
> reproductive potential of house cats is very secondarily affected by
> their selective advantages, with human will (birth control pills and
> emasculation) being important factors diminishing the reproductive
> possibilities of ordinary or out of fashion cats relative to fashion
> varieties, thus providing other mechanism for increase of proportions
> of new varieties. The influence of human hand in house cat
> reproduction suggests to me that natural selection finds here powerful
> opposition. Human caprice can also influence the change in variety
> proportions in alley and also feral cats, because many kittens borning
> from house cats which cannot find a home now form part of these
> groups. That human hand is behind the increase of proportion of
> fashion or new varieties may be attested by the fact that you can see
> a larger proportion of new varieties in rich countries (along with a
> greater proportion of exotic pets), with humans being more capable to
> buy expansive fashion varieties, than in poor countries, where kittens
> are mostly donated because most people will not pay for an ordinary
> cat, and can't afford an expensive one (and thus fashion or new
> varieties keep being uncommon).
>
> Regarding Jason's point, you are right that mammalian lips seem not a
> huge obstacle to teeth penetrating prey, because of being soft enough.
> However, if we accept carnivorous dinosaurs as having scales in their
> lips, lip flexibility would at least partially depend on the size of
> the scales. If bird beaks have something to do with reptilian scales
> after all, and if dinosaurs had similarly large scales, they would
> make their lips relatively less flexible, and lip scales would be
> prone to breaking as the teeth penetrated flesh. Now, if dinosaur lips
> possesed small scales, or lacked scales (one of these two would apply
> to crocodiles, after all), you would be right.