Along the same lines
a paper by Zusi 1993 showed a series of Galapagos finches (now considered tanagers, evidently) that ignored that tilt according to photo overlays of in vivo specimens (Fig. 1). Zusi preferred to have all the jugals horizontal when they should descend based on in vivo photos.
like storks and shoebills, do tilt the skulls down anteriorly, like dogs and ornithocheirids do. Some don’t. It’s best to get it right.
Not sure if this affects scores
in analysis. But if the jugal ‘descends’ or the quadrate ‘leans,’ some scores may change.
Zusi RL 1993. Patterns of Diversity in the Avian Skull. Fig. 8.9, pp. 391–437 in Hanken J and Hall BK, The skull, Volume 2: Patterns of structural and systematic diversity. University of Chicago Press, Chicago and London.