Re: CERATOP(S)IAN ARMS AND SEGNOSAURS

[Stan Friesen <swf@ElSegundoCA.ATTGIS.COM>]

From: morgan@montereybay.com (Morgan Family)
 ...
 > If (a) footprints do not lie and (b) they really are ceratop(s)ian prints 
 > (which someone on this list - I can't remember who - recently showed is very 
 > likely)

Me.

 > and (c) the foreprints are oriented closely together with a slightly 
 > duck-toed angle to them, as I have heard (which might rule out even a bow-
 > legged posture unless the dinosaur was fond of dislocating its wrists; the 
 > duck-toed condition would probably mean that the elbows were actually 
 > pointed inward - at least when the foot contacted the ground. Try it with 
 > your own arms!) I would be very interested in knowing how you fit this 
 > in with your theory, Rob. 8(=;u)=)
 > 

Duck-toed - nice term.

In trying it with my own arms, I found that with the elbow tucked in
near the rib cage, but not praticularly pointed inwards (in fact as
clse as I could manage to straight back), my hands naturally ended
up in just the right position to produce the trackways I saw pictures
of - slightly outside of the midline and slightly duck-toed. (At least
once I rotated my wrists to place the my palms flat to the ground).

As near as I can see, the suggestion of a horse-like gait in which the
humerus flexes slightly outward during the power stroke seems like
the most parsimonious reconstruction. This fits well with the trackways.

I *have* managed to combine a bow-legged posture with the correct hand
placement - but it *hurts* (extreme outward rotation of the wrist).
 > 
 > SEGNOSAURS! Are they really still categorized as theropods? If so, why?
 > 
Somebody found a putatively intermediate form which was clearly
a theropod.  This form is called Alxasaurus.

swf@elsegundoca.attgis.com              sarima@netcom.com

The peace of God be with you.