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RE: Making Lip of It
Jaime,
I'm glad you posted this article. My girlfriend is a science
illustrator and she has been motivating me to start drawing with more
frequency. I've started drawing dinosaurs again, but I've
been growing frustrated with this lip issue. It's not exactly a small
problem, as it has a dramatic effect on the way a dinosaur looks. I've read
through your article a few times and I have some things I'm hoping to
discuss with people more knowledgeable than myself.
In your article you state that the placement of the foramina seem to
indicate lizard-like tendenous 'lips' similar to those found on lizards. I
often found this somewhat convincing in the past, but after spending the last
few days looking at dozens of pictures of crocodilian and squamate skulls,
while at the same time reading arguments from others on this list, 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
Now on the other hand, so do some crocodilians. So, I don't find the presence
or lack of an overbite very convincing either way. What it does suggest, to me
at least, is that they would have been able to at least partially seal their
mouths without the aid of lips.
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
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
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? This leads me to my
next point: I suspect that most, if not all ornithodiran archosaurs were
'lipless' and this may have been why so many lineages tended to evolve a beak
of one form or another. Maybe a lipless mouth is a necessary precursor to a
beak. I suspect that a beak may have often started out has a hard covering on
the snout that gradually worked its way back along the jaws, replacing the
teeth in the process. But as you point out, a beak of this nature may not have
been able to coexist with lizard like lips. This seems to present an argument
against dinosaurs having lips since we know that many archosaur lineages
evolved beaks independently.
So, when I consider these points, I am inclined to depict most, if not all
dinosaurs without lizard like lips and I suspect the beaked, lipless depictions
of dromaeosaurids is the most probable. Of course, I am by no means an expert
on this subject, but since there is so much disagreement, I am forced to pick
one option or the other unless I intend to draw them with blank mouths.
Simeon Koning.
----------------------------------------
> Date: Sun, 18 Sep 2011 02:19:13 -0600
> From: qi_leong@hotmail.com
> To: dinosaur@usc.edu; Vert.Paleo.Mailing.List@listproc.usc.edu
> Subject: Making Lip of It
>
>
> I'm going out on a limb and posting my (sometimes) controversial opinion in
> regards to that perennial problem of dinosaur lips. In this, I will
> temporarily gush over Larry Witmer's biology work while at the same time
> taking an aim at a cherished childhood icon, "Crash" McCreery's
> "velociraptors" from _Jurassic Park_. The conclusions are anything but, but I
> had a lot of fun making the art. Check it out at my blog, or follow the
> direct link: http://qilong.wordpress.com/2011/09/18/making-lip-of-it/ . At
> over 3,500 words, it's my largest single piece written exclusively online,
> and represents the culmination of a few lines of data regarding jaw structure
> and soft-tissue analogies. As I state in the post, I'm an amateur and would
> appreciate positive criticism.
>
> 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)
>