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

Re:prolacertiformes as arboreal leapers,.



----- Original Message -----
From: "Larry Febo" <larryf@capital.net>
To: "David Marjanovic" <david.marjanovic@gmx.at>; "The Dinosaur Mailing
List" <dinosaur@usc.edu>
Sent: Sunday, March 18, 2001 3:35 PM
Subject: Re: Re:prolacertiformes as arboreal leapers,.


> >> PS....I`ve seen pictures of Tanystropheus depicted in a bipedal stance
as
> >> well. In primates, bipedalism came about as a consequence of
arborality.
> >> Perhaps a parallel development was the case for Prolacertiforms???
> >
> >Never ever -- unless you find a _brachiating_, tailless prolacertiform.
>
> Why do you think it had to be a "brachiator"???  It is my opinion that the
> presence of both horozontal and vertical substrates on which to locomote
> (which would be the case in an arboreal enviornment) might lead to more
> freedom of motion in the hips, as well as a more upright stance and
> parasagittal gait.

I may have misunderstood from something -- there is a hypothesis that we are
bipedal because we have brachiating ancestors who spent much of their lives
hanging vertically, so they simply kept that posture on the ground. Gibbons
indeed walk bipedally in the rare instances they come down from the trees. A
prolacertiform, being a sprawler, would need less, not even more, freedom of
motion in the hips; strictly parasagittal gait is disadvantageous for
climbers; if you mean a humanlike posture (vertical trunk) by "upright
stance", IMHO this is hardly feasible with short legs and a normal-sized
tail (I'm saying this with a sample of 1, so...). Climbing alone, without
brachiating, means that both hands and feet are used for locomotion, and
therefore secondarily terrestrial animals (such as baboons) will rather stay
quadrupedal.

BTW, there seems to be confusion about "scansorial" -- AFAIK this refers
strictly to climbing on tree trunks (not limbs), so woodpeckers and
squirrels are to a certain degree scansorial.

(Is there a simpler expression than "brachiating"? There is one in German,
and sometimes I wonder whether I use unneeded technical terms because I read
Nature, Science, JVP etc. all the time...)