Posture of *Edmontosaurus annectens*

["Brad McFeeters" <archosauromorph2@hotmail.com>]

I went to the Royal Ontario Museum on the weekend to make some observations 
on the dinosaurs, especially the hadrosaurines.  A few that I would like to 
discuss:

The mounted skeleton of *Edmontosaurus annectens* (ROM 867) in the alleged 
walking posture is unusual in that many of the dorsal ribs (no. 6-10) 
overlap distally on the visible side.  No. 7 is the most lateral, with the 
rest becoming increasingly medial as they move away from this rib.  There's 
also a noticeable gap where the neural spines above ribs 9 and 10 appear to 
be too far apart- the gap is almost the length of a neural spine.  These 
anomalies might disappear if the dorsal arch was straighted out some- this 
might have the effect of lifting the forelimbs above the quadrupedal level 
and making the animal more likely a biped.  Unfortunately, the anterior 
dorsal vertebrae are not visible in the display.  The skeleton of 
*Gryposaurus incurvimanus* (ROM 764) has a similar posture, but its ribs are 
spaced normally.  Perhaps these hadrosaurines did not have the same posture 
in life?  (Possibly relating to the subject of bipedal vs. quadrupedal 
hadrosaurines, I observed some interesting variation in the forefeet of 
various species.  In *E. annectens*, metacarpals III and IV are most 
strongly developed and appressed; metacarpal II is more slender and not 
appressed to III.  *Maiasaura peeblesorum* has all three slender and not 
appressed (they are in fact mounted as a bit divergent); and *Prosaurolophus 
maximus* (ROM 787) has II-IV all appressed.)

ROM 867 has the only truly droopy, dragging hadrosaur tail on display.  I 
was a little surprised that I could see no obvious places where the tail 
bones had been broken or disarticulated.  How is it universally known that 
no hadrosaurids dragged their tails?  ROM 867 as displayed has no ossified 
tendons over the tail, but I do not know if this is characteristic of 
*Edmontosaurus annectens*, or an artifact of preservation/preparation.

_________________________________________________________________
MSN Premium with Virus Guard and Firewall* from McAfee® Security : 2 months 
FREE*   
http://join.msn.com/?pgmarket=en-ca&page=byoa/prem&xAPID=1994&DI=1034&SU=http://hotmail.com/enca&HL=Market_MSNIS_Taglines