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Outcast Pterosaurs (was Arms into wings)



-----Original Message-----
From: Jaime A. Headden <qilongia@yahoo.com>
To: dinosaur@usc.edu <dinosaur@usc.edu>
Cc: larryf@capital.net <larryf@capital.net>
Date: Sunday, March 07, 1999 2:24 AM
Subject: Re: Arms into wings



>We certainly don't assume skin-gliding as in mammals and
>those kooky lizards and snakes would have been a part -- this requires
>long arms, which according to all forms of phylogenetic reasoning,
>would not have existed until that ancestral maniraptoran.>>
>
>Larry Febo wrote:
>
><Who is "We"?>
>
>  Sorry, I tried to edit that pronoun out of the text of the post, and
>did so elsewhere, but missed this one. Should read "As far as my
>studies show, _I and some others_ don't assume skin-gliding as in
>mammals and those kooky lizards and snakes would have been a part --
>this requires long arms, which according to all forms of phylogenetic
>reasoning, would not have existed until that ancestral maniraptoran."

OK, ...fair enough. You meant we of the "Orthodox" view, (or BAMM). I was
beginning to wonder at what level I was being left out...all
Paleontologists, all scientists,all of
humanity....Animalia??....(hey,...it`s been suggested!...8^). Anyway, thanks
again to everyone on this list that allow me to express my "unorthodox" view
and help me sort things out ....(one way or the other).

>
><What about my "Pterosaur to bird theory"?? Can`t it get ANY kind of
>recognition around here???.....(sheesh!)
>
>Pterosaurs had the long arms,...and the skin membranes...>
>
>  Not to put your theory down, but the skin of avian arms is very
>different from that of pterosaurs.

I`m not sure how that can be determined from the limited fossil evidence.
I`m assuming that the skin as well as any integumentary covering would in
fact be quite similar. Even the orthodox phylogeny has pterosaurs as a full
blown archosaur.


 >My phrase was put in the context of
>bird vs. mammalian gliding origins to flight and the extant gliding
>and flying pattern in lepidosaurs and mammals. I did not consider the
>pterosaurs, for one thing their different flying structures. There is
>a greater corollary, for instance, between pterosaurs and bats. Finger
>support of a wing membrane, or fingers at all.


Yeah,I guess most people think of bats when they see pictures of pterosaurs
with the large wing membranes. It used to be worse, in 1812, even
Sommerring, known as an anatomist and surgeon interpreted a pterosaur as
having a "batlike" attachment of the wing membrane from arms all the way
down to the feet. (see Wellnhofer`s interesting book "Prehistoric Flying
Reptiles")
But heck, even Chickens have a rudimentary wing membrane. I notice this
every time I cook one.


> Pterosaurs developing
>from short armed and long legged to the reverse, as in birds, should
>be significant, since this is paralleled in birds, but the structure
>of the ankles and arms are different in the evolutionary paths of both
>when we get down to it; they went through similar solutions to the
>same problems, but not identical solutions, and at the moment they
>split, that was it.


Padian`s ( and I assume the orthodox) view has it that both Pterosaurs and
Birds developed from cursorial theropod ancestors. In this case, I believe
he is arguing for the homology of the bird-pterosaur ankle. He points out
Lagosuchus (with it`s advanced mesotarsal ankle) as a possible pterosaur
ancestor.


>There is a line leading from small short armed
>theropods to birds that is not matched in pterosaurs. All pterosaur
>ansectors or possible ones had fully different morphology of the
>shoulder, ankle, and pes than in birds and theropods, which are
>closely matched.


Well , again,...Padian states "The detail of many resemblances between
pterosaurs and modern birds is uncanny,..."   And here he is spreaking of
all those items you mentioned (shoulder, ankle and pes).(see Padian`s "The
Origin of Pterosaurs")

Then there is the view that pterosaurs arose from prolacertilian ancestors
 with which I agree). As these forms were evolving into a flying condition,
many flight related specializations don`t show,  or are only in their very
early initial configuration. See Dave Peter`s "Pterosaur Webpage". He states
that Cosesaurus is considered as a close sister group to pterosaurs. Padian
(and others) consider pterosaurs as close sister group to the dinosaurs. I
think they are both right, but in the order
Prolacertiform>Pterosaur>Theropod (Bird).


>
>  Additionally, pterosaurs possess not only a fourth "flight" digit,
>but the structure of the "hand" is so highly different in even the
>most primitive pterosaur (*Preondactylus*) that bird/pterosaur
>homology of flight apparatus cannot be approached on similar grounds
>except for the base dynamics that all flying vertebrates have (bats,
>birds, pterosaurs, lemurs, fish, and squamates).


Yes, the pterosaur manus seems very different from birds, but things can ,
and do change dramatically. I have not, as yet, seen any proof that there
exist any bones in the bird manus that do NOT exist in the pterosaur
manus.So, I can`t conclude that a bird manus cannot be developed from a
pterosaur manus. Although there is much fusion of certain carpal elements,
and hence perhaps some confusion. The bird manus seems to differ in the loss
of previously existing bones (including the long pterosaur wing digit), and
fusion of others (in modern birds).


>
>  That's all I will say on the matter. This applies to the homology of
>flight, whichw as what I was talking about in the previous post, not
>evolutionary relationships. That's your tackle to make, to use an
>American football term.
>


Well, fossil evidence in this particular area may be scant, but I think that
eventually, Pterosaurs are going to get the recognition they deserve,
...that is , not just flying lizards,(sitting on the sidelines  8^)  but
something much closer to dinosaurs in the evolutionary shceme of things.