Question - problem in Senter 2006?

[Jason Brougham <jaseb@amnh.org>]

I have a question for experts on Senter (2006) Comparison of Forelimb Function 
Between Deinonychus and Bambiraptor (Theropoda: Dromaeosauridae) JVP 26 
(4):897-906.

I've been working on a Microraptor anatomical model using Senter 2006 as a 
primary source for a few weeks now. 

I noticed some anomalies in Senters discussion of Bambiraptor but just this 
moment the full magnitude of the possible error dawned on me. I ask experts on 
the DML to confirm my understanding.

In the text Senter notes that the humerus can be elevated to a nearly 
horizontal position, and that this result largely agrees with Gishlick 2001. 

In Senter's Figure 1,  the second figure, labeled cranial view, the humerus 
position marked e (e for elevated humerus) seemed to me to show the humerus at 
80 degrees above horizontal, considering the orientation of the coracoid and 
scapula.  The figure appears to be turned on its side to fit on the page. Just 
now I realized that Senter has presented this figure as a life position, not 
turned on its side.

In other words, he has placed the glenoid pointing straight down ventrally, and 
the sternal process of the coracoid turned to point medially. Thus the scapula 
lies ventrolateral, not dorsal, to the coracoid.This explains why, in the 
figure to the left of this, the coracoid stands dorsally to and  high above the 
scapula. 

In fact the sternal process of the coracoid should point ventrally, and 
articulates with the coracoid groove of the sternal plate along the anterior 
sternal margin, as in IGM 100/985 (fig 3 in Norell& Makovicky (1997). The 
ventrally pointing sternal process of the coracoid is confirmed by the 
configuration of dromaeosaur coracoids and sterna in Norell&Makovicky (1999), 
Jasinoski et al. (2006), Godfrey&Currie (2004) and many deinonychosaur 
specimens found in articulation.

If we turn Senter's figure 1 so that the sternal process points ventrally then 
he has, in fact, found a range of motion for the humerus that shows an 
elevation of the humerus at 80 degrees ABOVE horizontal! He has also found that 
the humerus can't be depressed much below the horizontal. Also, the figure to 
the left, previously called lateral view must now be considered a dorsal view.

Can anyone tell me if I've made any mistakes in my interpretation of Senter 
here?

Thank You,


Jason Brougham
Senior Principal Preparator
American Museum of Natural History
jaseb@amnh.org
(212) 496 3544