Surely the assumption is that the habitual posture should be the one
with minimal stress everywhere? At least that's how I read Christian
& Heinrich 1998.
Sorry... in fact I didn't. _Because_ the stress of longitudinal compression
is much less than that of bending, the cross-sectional area of the
intervertebral discs must increase (towards the base of the neck) faster in
an animal with a habitually horizontal neck than in one with a habitually
vertical one. Consequently, a horizontally carried neck will appear greatly
overdesigned for a vertical posture. This discrepancy is the subject of
Christian & Heinrich (1998) and Christian (2002).
I have challenged the entire quality assurance team to a
Bat-Leth contest.