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

Re: T&F talks, SVP, Pteraichnus




Jaime A. Headden wrote:

> David Peters (davidrpeters@earthlink.net) wrote:
> The humerus is left as horizontal,

Why?

> Taxa showing
> nearly horizontal postures include ......, and I am betting one or two others
> based on relatively good skeletons (including *Quetzalcoatlus* sp., but
> this is based on Paul's skeleton and not my measuring).

Quetz is capable of bringing the torso near horizontal, but not with the 
humerus horizontal.  That requires that the elbow be highly flexed and raised 
well above the shoulder (there are overlapping bone ledges at the shoulder and 
elbow that
can mechanically support the weight of the quetz when it is in this position).  
Walking with the torso horizontal would require a reversal in the direction of 
humerus/shoulder rotation that would be possible but seems improbable.  With
quetz's relatively inflexible and extraordinarily long neck, I suspect keeping 
the cg aft of the manus prints while in this posture might be an interesting 
excercise.

>  The problem: I did these measurements from scaled figures I drew based
> on measured specimens. Most specimens were measured by using photographs
> and scaling everything exactly to the size I needed for the skeletal
> reconstruction itself, rather than numbers in a book. So my estimates for
> *Q.* sp. and *Pteranodon* are based off Paul's reconstruction, the latter
> being a composite, but there are specimens with both arms and legs so I am
> confident it's accurate;

Send me offlist the Qsp dimensions you used, and I will tell you if they are 
accurate.