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RE: Making Lip of It



  I do not think the exposed teeth of so-called "fishing" pterosaurs like 
ornithocheirids ("anhanguerids") should be a problem. It may very well be that 
their extreme exposure to moist environments and being fish-eaters provides 
them the necessary moisture to prevent drying of the gums or whatever. It 
should be especially interesting to extrapolate extraoral tissues in an animal 
like *Pterodaustro guinazaui*, given that the lower jaw overlaps the upper in 
all dentition, but was also apparently exposed to very wet environments (as a 
"filter-feeder"). 

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: Thu, 22 Sep 2011 14:46:45 -0400
> From: martyniuk@gmail.com
> To: dinosaur@usc.edu
> Subject: Re: Making Lip of It
>
> How do we know pterosaurs didn't have lips? ;)
>
> Ok, some of them would have had some very interesting appearances if
> they did... But the species with the most outlandish teeth
> (ctenochasmatids, ornithocheirids) were probably using them to catch
> fish anyway, so they would have been wet much of the time.
>
> Matt
>
> On Thu, Sep 22, 2011 at 2:37 PM, Sim Koning <simkoning@msn.com> wrote:
> >
> >
> >
> >      I only have time at the moment for a brief response, but I wanted to 
> > cover this at least.
> >
> >> *Kaprosuchus* and *Simosuchus* do not belong to the freshwater clade of
> >> crocodyliforms, which contains the crown-group, nor to the marine clade
> >> (which may or may not be the sister-group of the freshwater clade).
> >> Their terrestriality is inherited straight from the ancestral archosaur
> >> and beyond. I'm not going to speculate on whether they had lips, except
> >> to note that their teeth may have benefited from protection against
> >> drying out.
> >
> >      I have a hard time imagining this guy with lips
> >
> > http://en.wikipedia.org/wiki/File:Kaprosuchus_2.jpg
> >
> >      This argument also seems to ignore the fact that there were many, many 
> > pterosaurs flying around with exposed teeth; some of these were inland 
> > species such as the Istiodactylids. It seems to me that flying around 
> > through warm air would be a great way to dry your teeth out, yet this 
> > doesn't appear to have presented any kind of problem for them. Then we have 
> > (what I must assume) were lipless taxa such the aforementioned Kaprosuchus. 
> > There were also the various tusked or fanged animals throughout history we 
> > should consider. Smilodon spent their lives with their most important set 
> > of teeth hanging out of their mouths. Wild boars are a modern example with 
> > jutting tusks that they use as weapons and digging tools. Elephants aside, 
> > I think the question should be whether or not the overbite seen in 
> > dinosaurs would be sufficient as a seal for the mouth.
> >
> > Simeon Koning
> >
> >
> >
> >
> > ----------------------------------------
> >> Date: Thu, 22 Sep 2011 09:56:11 +0200
> >> From: david.marjanovic@gmx.at
> >> To: dinosaur@usc.edu
> >> Subject: Re: Making Lip of It
> >>
> >> > [...] I'm leaning more and more to the lipless side of this debate.
> >> > Though I do have problems with some of the arguments being put
> >> > forward by both sides. For example, in old post on this list Tracy
> >> > Ford argues that the presence of an overbite strongly suggests a
> >> > lipless morphology, since lizards tend to have interlocking teeth and
> >> > no overbite. However, from what I can tell, geckos have an overbite
> >> > rather similar to that of some dinosaurs.
> >> >
> >> >
> >> http://digimorph.org/library/pop.htm?/specimens/Gekko_gecko//specimenlarge.jpg
> >>
> >> I don't see why an overbite should mean there can't be lips. Part of the
> >> function of lips is to protect the teeth from drying out, and that still
> >> applies to the upper teeth in an animal with an overbite.
> >>
> >> The ivory from forest elephants is said to be much better than that from
> >> savanna elephants because the tusks of savanna elephants are exposed to
> >> much drier air.
> >>
> >> > Arguments that revolve around foramina don't seem to help much. If
> >> > they are diagnostic of anything, it seems to be degrees of
> >> > sensitivity and vascularity of the skin around the jaws. The nutrient
> >> > foramina found around the jaws of spinosaurids follow a single
> >> > channel until they reach the tip of the snout, where they begin
> >> > spread out or form several rows. This suggests to me that the
> >> > foramina had more to do with sensitivity of the mouth than to the
> >> > presence of lips. Deinonychus has a double row of foramina on the
> >> > maxilla while they seem (to me) to be lacking on the rostrum. So
> >> > perhaps they lacked lips altogether and possessed a keritanous
> >> > proto-beak? I know you do not like this idea, but splitting the lip
> >> > tendon/ligament seems only to be a problem if you assume they had
> >> > lips in the first place.
> >> >
> >> >
> >> http://digimorph.org/library/pop.htm?/specimens/Osteolaemus_tetraspis//specimenlarge.jpg
> >>
> >> Foramina can mean plenty of different things. Squamates have foramina
> >> for squamate-only slime and (in some cases) poison glands. Crown-group
> >> crocodiles have foramina all over their snouts for water pressure
> >> receptors. Mammals, and maybe other theropsids, have foramina for nerves
> >> associated with whiskers, and so on...
> >>
> >> > If you look at the jaws of a dwarf crocodile, you will notice that
> >> > they are practically covered in foramina. I know some have argued
> >> > that the liplessness of crocs is probably due to their aquatic
> >> > nature, but then I have to ask why this did not present a problem for
> >> > terrestrial crocs such as Kaprosuchus or Simosuchus, both of which
> >> > were fully terrestrial, with one likely an herbivore.
> >> >
> >> > http://en.wikipedia.org/wiki/File:Simosuchus_clarki_skull.jpg
> >>
> >> *Kaprosuchus* and *Simosuchus* do not belong to the freshwater clade of
> >> crocodyliforms, which contains the crown-group, nor to the marine clade
> >> (which may or may not be the sister-group of the freshwater clade).
> >> Their terrestriality is inherited straight from the ancestral archosaur
> >> and beyond. I'm not going to speculate on whether they had lips, except
> >> to note that their teeth may have benefited from protection against
> >> drying out.
> >>
> >> > In the case of Simosuchus, the placement of foramina does not seem to
> >> > differ greatly from what we see in some dinosaurs such as
> >> > Deinonychus. You may notice that there is a cluster of foramen
> >> > located on the maxilla, while they are lacking on the rostrum.
> >> > Perhaps the tip of the snout was covered with a hard keritanous
> >> > covering, perhaps a sort of proto-beak?
> >>
> >> Why?
> >
> >