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Posture of *Edmontosaurus annectens*
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.
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