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RE: Making Lip of It



This is the question that cats invoke: Why, exactly, can't an animal be 
partially lipped? Again, how do you tell if something does and does not have 
lips, aside from some practicality of _covering the entire tooth_? The last 
issue should be known to be largely irrelevant, as the elemental problem here 
is that lips have yet to be shown to preserve or conceal _teeth_.

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)


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> Date: Fri, 23 Sep 2011 11:05:56 -0400
> From: simkoning@msn.com
> To: martyniuk@gmail.com; dinosaur@usc.edu
> Subject: RE: Making Lip of It
>
>
>      I think I'm comfortable saying that most (if not all) pterosaurus almost 
> certainly did not have lips. A great many of them had very long interlocking 
> teeth similar to those of a gharial. It seems that their length and/or angle 
> of projection would definitely preclude the lips we see in lizards today. 
> Then of course we have the more derived forms with no teeth at all. It seems 
> improbable to me that they would go from a 'gharial-toothed' form with big 
> fleshy lips to a bird like beak with no clear transition. I can think of a 
> few more reasons, but for me at least, these two are enough.
>
> Sim
>
>
> ----------------------------------------
> > Date: Fri, 23 Sep 2011 08:28:14 -0400
> > Subject: Re: Making Lip of It
> > From: martyniuk@gmail.com
> > To: simkoning@msn.com
> > CC: dinosaur@usc.edu
> >
> > "Pterosaurs seem to have been a largely toothed but lipless group with
> > some non-fishing inland forms"
> >
> > Again, is there any actual evidence for this assertion? AFAIK the
> > evidence is just as equivocal for non-beaked pterosaurs as it is for
> > non-beaked dinosaurs.
> >
> > Matt
> >
> > On Thu, Sep 22, 2011 at 10:23 PM, Sim Koning <simkoning@msn.com> wrote:
> > >
> > >
> > >
> > >
> > > To reiterate my point about pterosaurs: there were insectivorous and 
> > > toothed inland species (some Istiodactylids) that probably weren't making 
> > > a regular habit of dunking their heads into water. Even the species that 
> > > were fishing would have been doing so in saltwater, something that tends 
> > > to rapidly desiccate tissues. Plus I doubt they spent their *entire* day 
> > > soaking their heads in sea water, as I'm sure they would have needed to 
> > > roost at some point. Kaprosuchus was most likely a terrestrial croc with 
> > > what was apparently a largely terrestrial ancestry, and it almost 
> > > certainly didn't have lips. Then there are the numerous mammalian 
> > > examples with exposed teeth despite the fact that they are not easily 
> > > replaced. I really don't think tooth dessication was that much of a 
> > > problem at all for most animals with exposed teeth. Nor is a dry mouth 
> > > for that matter: parrots have very dry mouths as they spend most of the 
> > > time with their mouths partly open, and they are *dinosaurs*. In fact, if 
> > > a parrot has a wet tongue it is usually a sign of illness. I really see 
> > > no barrier to a dinosaur evolving a largely dry mouth, or exposed teeth, 
> > > or both.
> > >
> > >
> > >
> > >
> > > What can phylogenetic bracketing tell us? If we look at terrestrial 
> > > crocodylopmorphs such as Sebecus and Kaprosuchus, we see jaw morphology 
> > > with interlocking teeth that would not have left much room for lizard 
> > > like lips. Pterosaurs seem to have been a largely toothed but lipless 
> > > group with some non-fishing inland forms. modern birds have beaks as did 
> > > many dinosaurs, many of which seem to have evolved independently. 
> > > Kaprosuchus seems to have had a keratinous 'bumper' of some sort on the 
> > > tip of the snout. Perhaps this is how the typical archosaurian beak 
> > > started out? I can see the advantage in having a hard covering on the 
> > > parts of the the mouth that were most prone to abrasion and injury. All 
> > > this suggests to me that 'liplessness' was the basal condition for most 
> > > of Archosauria. Perhaps a lack of fleshy lips allowed for the rather 
> > > large sharp teeth we see in so many predatory archosaurs. Lizard like 
> > > lips may very well have been more trouble than they were worth for a 
> > > great many archosaurs. This is something I have yet to see addressed. The 
> > > assumption often seems to be that lips would have been beneficial for 
> > > predatory archosaurs, and so no good reason can be found for why they 
> > > would be lacking. If you look at the open mouth of a lizard such as 
> > > Komodo dragon, you will notice that their teeth are not even visible 
> > > despite their large size. If a dinosaur such as Deinonychus had lips of 
> > > this sort, it would have looked toothless when it opened its mouth. The 
> > > reality is that the sharp teeth of Varanids actually tend to lacerate the 
> > > tissue surrounding them. I suspect that this would have been a problem 
> > > for many theropods, not an advantage.
> > >
> > >
> > > I suspect the typical pattern that independently lead to beaked jaws in 
> > > so many archosaur lineages may have been something like this:
> > >
> > > 1. Lizard lips with interlocking teeth > 2. Lizard lips covering jaws 
> > > with an overbite > 3. Reduced lips with an overbite > 4. No lips with 
> > > exposed teeth (most of Archosauria) > 5. Exposed teeth with a hard scaly 
> > > covering on the skull > 6. Teeth with a rostral 'proto-beak' > 7. A 
> > > reduction in size and/or number of teeth > 8. A toothless beak.
> > >
> > >
> > > Simeon Koning
> > >
> > >
> > >
> > >
> > >
>