Table 1. Comparison of interpretation of selected morphology from previous and current studies of Pachyrhachis problematicus. Ue1-ue5 refer to the elements illustrated in figure 5 of this study. See Figure 2 for illustrations and interpretations of previous studies.  

Haas 1979, 1980a Caldwell and Lee 1997 Zaher and Rieppel, 1999b This Study
Postfrontals Jugals Broken displaced anterior ectopterygoids Ventral portion of postorbitals (ue1&ue2)
Not applicable  Postfrontal fused to postorbital Crushed frontalis decensus Anterior portion of ectopterygoid (ue3)
Anterior portion of left ectopterygoid Posterior left maxilla Not applicable Anterior portion of left ectopterygoid 
Posterior portion of left ectopterygoid Ectopterygoid Not applicable Posterior portion of left ectopterygoid
Right ectopterygoid Posterior right maxilla Posterior right maxilla Posterior right maxilla
Not applicable Medial processes of postorbital Not part of postorbital Possibly crushing of parietal table (ue4&ue5)
Stapes Tentative squamosal Stapes Stapes
Not applicable Stapes Paroccipital process of opisthotic Stapes
Not applicable Vertically oriented quadrate Posterventrally inclined quadrate Posteroventrally inclined quadrate 
Not applicable Two mental formina One mental foramen One mental foramen 
Not applicable Broad lateral profile of quadrate No suprastapedial process of quadrate No suprastapedial process of quadrate
Not applicable Broad lateral profile of quadrate More Macrostomatan-like quadrate Stylohyal process on ventral medial margin
Not applicable Exoccipitals do not contact Unknown  Unknown