Nyctosaurus pectoral girdle

[David Peters <davidrpeters@earthlink.net>]

Although I understand the differences in articulation between the
scapula and spine in Pteranodon and Nyctosaurus, I am still perplexed by
Chris Bennett's statement that in Nyctosaurus the scapula did not
articulate with the notarium.

In Chris's latest paper, he identifies a notarium in Figure 3. So there
is a notarium in Nyctosaurus, not just a series of unconnected
vertebrae.

In the Nebraska Nyctosaurus (UNSM 93000 - articulated in dorsal view)
one scapula is disarticulated, and slightly off the spine, but the other
is aligned laterally with its broad proximal end  at the midline.

In the Sternberg Nyctosaurus (SMM 11311 - torso articulated in ventral
view) both scapula are oriened laterally and would appear to contact one
another but for the presumed intervening set of neural spines.

Perhaps there is no peg and socket arrangement, as in Pteranodon, but
surely these are signs of articulation.

As an aside, there are a large number of small and large pterosaurs with
short and long scapula which articulate with a more or less fused spine.
The question becomes, at what point do we call a set of neural spines
with funny-looking tops and interconnections a notarium? And at what
arbitrary angle in the phylogenetic lateral opening of the scapulae do
we draw the cladistic character line and say this anterior orientation
is primitive while this lateral orientation is derived? There is a
spectrum of possibilities out there.

David Peters
St. Louis