Re: Bipedalism

[Dinogeorge <Dinogeorge@aol.com>]

In a message dated 98-03-26 02:36:41 EST, rjmeyer@ix.netcom.com writes:

<< Could this be a part of the explanation for bipedalism in theropods?  When
the "dawn theropods" began to stand up, did this behavior give them a greater
range of vision, enabling them to see higher and farther than before?  If so,
then this behavioral trait would have an adaptive advantage, which would also
select for any physical traits that would help this behavior to develop.
Perhaps this explains why theropods were so successful as a predator. >>

The problem with this scenario is that the obligatory bipedalism of theropods
doesn't follow compellingly from the occasional bipedalism of which most
otherwise quadrupedal animals are capable. Just because an animal can stand on
its hind legs to have a look around (or for whatever reason--to forage, to
mate, to run around a bit, etc.) doesn't mean its descendants are going to
undergo natural selection for this character at the expense of being
quadrupedal. Why should they? They can have both advantages at the same time
when they're quadrupedal and capable of standing.

Besides, getting up on their hind legs to see stuff would make them more
visible to their enemies.

In the BCF scenario, as I've said here many times before, theropods were
bipedal because their forelimbs had become too modifed for climbing, gliding,
and/or flying to make do for walking. This is a perfectly reasonable and
natural explanation for theropod bipedalism.