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

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.
 
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).



                                Silvio Renesto

-

"Before being enlightened,   hard work; after enlightenment, hard work"
(Guo Yunshen).

Dr. Silvio Renesto
Dipartimento di Scienze della Terra
Università degli Studi di Milano
via Mangiagalli 34
I 20133 Milano
Italy

phone +39-0223698232
fax  +39-02-70638261

e-mail:    renesto@mailserver.unimi.it

or/and     Silvio.Renesto@unimi.it