Re: Sauropod feet and ancestry ...

["Jaime A. Headden" <qilongia@yahoo.com>]

Mike Keesey wrote, on my comment on the possible
weight-related similarity of segnosaur and sauropod
feet:

<<Perhaps it's a graviportal issue?">>

and Matthew Bonnan (who else?) replied:
 
<Well, remember that graviportal animals have a number
of features besides modifications in the feet. The
limbs of graviportal animals, like sauropods or
elephants, are held as vertical columns during most of
the gait. This is because bone works best in
compression, and therefore the weight of the animal
can be safely supported and moved with this system. 
Also, the femur tends to be longer than the crus
(tibia and fibula).
 
I am not aware of the exact proportions of segnosaurs,
but they do not strike me as inherantly graviportal
(maybe medioportal?). I have to admit the feet of
segnosaurs do look an awful lot like those of
prosauropods, but since other characters appear to
unite them with theropods, and since it was mentioned
that the first digit does not make contact with the
tarsus (as in prosauropods), this foot condition may
be due to variation on the saurischian pes plan
(speculation here, to be sure).>

  *Segnosaurus* has a longer femur than tibia, at
least according to all the papers on the subject and
Perle's measurments in a single specimen. *Alxasaurus*
has a slightly longer tibia than femur, and I have no
idea of *Beipiaosaurus*. The known leg refered to
*Therizinosaurus* (Barsbold, 1979) is an incomplete
tibia?

  Now, all graviports are quadrupeds, and to my
knowledge, all bipeds (like therizinosaurs) fit into
the cursor or subcursor classes, but lacking an
education on what qualifies as what in these classes,
I can't comment further. Help?

===
Jaime A. Headden

"May I lure us, ere the mote ends us?"

Qilong, the we---is temporarily out of service.
Please check back when the phone lines are no
longer busy.
_________________________________________________________
Do You Yahoo!?
Get your free @yahoo.com address at http://mail.yahoo.com