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

Re: Ceratopsians: sprawling or straight?



Seems I need to address this subject, both due to the erroneus claims that
continue to confuse the issue of ceratopsid arm posture, and to garbled
notions regarding my work. 

Per Christansian and I are wrapping up a major MS on ceratopsian locomotion.
It shows that their forelimbs 
were configured to work in an erect manner, with the hands directly beneath
the shoulder joints and separated by only one and a half hand widths
(measured from the inner edge of the hands) - as per the trackways. This is
an essentially mammalian arrangement, for example wildebeest walk with their
hands well separated, more so than the hindfeet. 

A few ceratopsian shoulder joints are crushed, resulting in a false lateral
orientation to the glenoid (this includes the Milwaukee Torosaurus element
Johnson & Ostrom studied). In uncrushed glenoids the scapular portion of the
glenoid actually faces partly medially, hardly expected in a nonerect arm! 

There will be no presentation on this subject at Dinofest III. How do those
wacky paleorumors start? 

The many skeletons mounted and restored with the arms more sprawling and the
hands separated by as much as four hand widthes are mere fantasies. For
example, the St Paul skeleton has the hands separated by three hand widthes,
twice what the trackways record. As for the hindfeet, in the trackway they
nearly touch on the midline, in the St Paul mount the feet are widely
separated. IF someone seems to think their measurements confirm that the St
Paul skeleton fits the trackways, I suggest they check their metric tape for
accuracy, and learn some geometry along the way. As for the Milwaukee
Torosaurus mount, it is even worse, because the feet are even further apart!
The idea that these skeletons are in any way in accord with the best trackway
is nonscientific, and just plain wrong. What is unfortunate is that none of
those responsible for these skeletons is making the effort to actually
remount them to fit the trackways. 

GSPaul