[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re:prolacertiformes as arboreal leapers,.



-----Original Message-----
From: Renesto Silvio <renesto@mailserver.unimi.it>
To: Larry Febo <larryf@capital.net>
Cc: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Thursday, March 22, 2001 9:42 AM
Subject: Re: Re:prolacertiformes as arboreal leapers,.


>At 11.18 16/03/01 -0500, you wrote:
>>
>In primates, bipedalism came about as a consequence of arborality.
>>Perhaps a parallel development was the case for Prolacertiforms???
>>
>If we accept that Protorosaurus and Prolacerta were primitive
>prolacertiforms, then they do not look arboreal.


I`m not sure I follow the logic here. (Why does "If we accept that they were
primitive prolacertiformes..."precede they don`t look arboreal???

At any rate, they do look so to me. In general body plan, they appear quite
lizardlike, and lizards can climb quite well. The divergent toes might have
been quite capable of grasping cycad bark, and might have been a "specialty"
for climbing along Cycad branches along the midrib. (I have speculated as
such for pterosaurs as well, but have not as yet looked into the matter in
detail,....it`s "on the agenda" though). Of course I am overlooking the
"largish" size of the holotypes Protorosaurus (at 1-2 meters) and Prolacerta
(at 1 meter long), which may have adopted a more terrestrial habitat, but
again,....surely they must have had smaller family members, that cou;ld have
been strictly arboreal?? ...(and of course, the smaller representatives are
less likely to get preserved, especially in an arboreal
enviornment...unfortunately).


>Overall morphology of prolacertiforms does not seem suited for scansorial
>life and (to me) it does not suggest arboreal ancestors.
>This does not mean that small and advanced prolacertiforms weren't able to
>climb, anyway.
>Chlamydosaurus (Australian frillneck lizard) actually lives on tree
>branches and runs bipedally on the ground to catch preys.
>
>>PS....I`ve seen pictures of Tanystropheus depicted in a bipedal stance as
>>well.
>
>The mighty Tanystropheus is a weird animal indeed, and very difficult to
>categorize concerning mode of life.
>The picture (or better, his author) suggests that  the elongate, metapodial
> fifth toe could have been spread posteriorly to increase support and
>balance in a bipedal digitigrade posture, acting  like the high heel of
>ladies' shoes.
>The neck seems to me so long and heavy to  create serious problems of
>balance unless it was so stiff to be kept easily in a vertical position
>without muscular effort, with the head neck and trunk all vertically placed
>straight over posterior limbs in a human fashion (just as in the
drawing!!).
>Having seen first hand some exquisite new specimens (sigh, only seen) there
>are little doubts that the neck was really stiff, and the way in which the
>neck is bent dorsally (with the cervical ribs spreading out in a
>spring-like fashion) suggests the presence of a powerful dorsal ligament.
>
> However, I still have doubts about a Tanystropheus in a vertical posture
>(and also about the high heel toe).



Tanystropheus,....could it have been vegetarian?? Perhaps it`s habit was to
"climb" up a trunk with it`s forelegs,keeping it`s feet on the ground in a
bipedal stance, and chest against the trunk in order to reach whatever
foliage it could with that long neck? It`s all speculation, but surely a
creature with such an atypical body form must have had some specific
enviornmental niche that could be figured out on examination of all the
possibilities???