Re: sauropod facultative sprawl?

["James Farlow" <farlow@ipfw.edu>]

>>> David Marjanovic <david.marjanovic@gmx.at> 9/29/2011 6:49 AM >>>
>  Wow. Is there any way to know whether tracks with wider-guage
>  forelimb placement versus narrower-guage forelimb placement come from
>  different taxa, or are these trackways too generic (so to speak)?

They're always attributed to different taxa -- Diplodocimorpha vs. 
Titanosauriformes (the broadest ones are attributed to titanosaurs). 
This fits the femur shapes of those sauropods.


Farlow: Well, no, trackway gauge as usually defined isn't what I was talking 
about.  Trackway gauge has to do with placement of pes prints in particular 
with respect to the trackway midline. In narrow gauge trackways the left and 
right pes prints are quite close to, or even overlap, the trackway midline, 
while in broad gauge trackways they are more widely separated from the midline, 
so that you can run a tape or something along the trackway midline without 
hitting the inner sides of pes prints. And as Mr. (or Dr.? I mean to give no 
offense) Marjanovic says, wide gauge trackways in this sense seem to reflect 
the femoral construction of titanosaurs.

What I was talking about is trackways in which manus prints (particularly the 
centers of manus prints) are positioned farther away from the centers of their 
corresponding pes prints.  There are some narrow gauge (as defined above) 
sauropod trackways (e.g. the ichnogenus _Breviparopus_; compare this with the 
ichnogenus _Brontopodus_)  that are like that.  Whether this is related to 
relative width of the body at the shoulder vs. the hip, or whether the beasts 
slanted hindlimbs inward more than forelimbs, or whether there was more of an 
outward kind at the elbow than at the knee, I wouldn't care to say without 
looking into this more than I care to do at the moment.  But I thought I should 
mention it.