UV light vs. LCA (last common ancestor) approach to flapping flight in birds

“The neural spines of the 16th to 22nd presacral vertebrae in the Berlin Archaeopteryx are bridged by interspinal ossifications, and form a rigid notarium-like structure similar to the condition seen in modern birds. this reinforced vertebral column, combined with the extensive development of air sacs, suggests that Archaeopteryx was capable of flapping its wings for cursorial and/or aerial locomotion.”

Schwarz et al. did not perform a phylogenetic analysis
nor did they mention anything about the elongate locked down coracoid present on this specimen. In the large reptile tree (LRT, 1445 taxa, subset Fig. 1) the Berlin specimen of Archaeopteryx (MB.Av.101) nests at the base of all flapping birds, including the Enantiornithes, the first clade to split off. As in the amniotic egg issue, the last common ancestor is where you find the genesis of traits common to all descendant taxa. So, Schwarz et al. are correct: the Berlin specimen is indeed close to the origin of flapping flight.

It’s not the reinforced vertebral column
that determines if a bird (or pterosaur) flaps or not. It’s the elongation of an immobile coracoid these two flapping clades share in common at the genesis of this behavior.

Distinctlively different
due to lacking a coracoid, bats employ the hyper-elongation of the clavicle to do the same thing by convergence.

One more thing…
if possible, don’t freehand your reconstructions (Fig. 2) and don’t redraw freehand reconstructions from Wellnhofer 2008 ~ especially if you’re going to go through all the trouble of extracting more precise data on a fossil than has been recovered before. Do your own more precise bone tracings and reconstructions!