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Unwin's ternary diagram question



A few years back (2001?) David Unwin was showing a ternary diagram based on 
femur, tibia and metatarsus lengths, I think. Only saw it briefly in a PPT 
presentation. Does anyone know if it has been published?

I bring it up because I just finished playing with Jim Clark's ternary diagram 
(Nature Feb 26, 1998) of the three digits in pedal digit 3 of pterosaurs and 
birds. The spread is a little larger than Jim lets on. Batrachognathus comes 
out on top of the swift. MPUM 6009, the basal pterosaur, comes out below and to 
the right of rhea. Austriadactylus joins the most of the birds in the middle. 
The reduction to a disc of p3.2 in most pteros moves most of them to the right 
of the diagram, as Clark indicates, but the trickling few with all the 
variation were left out. 

IMHO the difference lies more in the way birds sit on branches without using 
their hands, while most pterosaurs appear better suited â?? from the golf grip 
on the lateral pedal PILs + their hand claws â?? to cling to tree trunks. In 
other words, the abilities and niches of pteros and birds probably cannot be 
compared on the basis of the proportions of pedal digit III. 

David Peters
St. Louis