On the dil-petiolaris vs petiolaris discussion, I'll probably go to my grave not fully grasping Sean Spence's taxonomic interpretation of the differences. IIRC, however, I had similar confusion w/ Andreas F. explanation of another petio (possibly the narrow leaf D. ordensis?). While I can handle ID'ing many/most plants, taxonomy is not one of my strong points.
I would definitely default to Travis & the others before quoting me .... (although I do think the post in quoted thread is accurate)