I didn't even realize it was different from the others I was photographing till I got home...

Am I correct in thinking this is the same gall Ron Russo calls the Pinched Leaf Gall Wasp on pg. 168?

It's the same as Ron's pg 168, figure 128, "Pinched Leaf Gall Wasp." If Ron gets to update his book some day, the gall will have the name Andricus bakkeri. He has Lyon's paper now and agrees it's the same species.

Russo 2006 mentions Oregon oak and the 1984 Lyon article mentions Q. garryana [ditto], Q. engelmanni, and Q. dumosa.

Are there other hosts?

Galls that are on Q. dumosa are usually on other scrub oaks as well. Most scrub oaks in CA where called Q. dumosa until around 1982, and it may not have been until the 1990's that Q. berberidifolia was more widely accepted as the name of a scrub oak that is widespread in CA. Specimens in many herbaria are still labeled Q. dumosa even if they probably aren't. Scrub oak taxonomy is confusing and probably not fully resolved, but in general the same galls occur on Q. berberidifolia, Q. cornelius-mulleri, Q. dumosa, etc.

Here's some useful reading on scrub oaks: http://tchester.org/plants/analysis/quercus/scrub_oaks.html

Thanks!