Found at the Hole in the Wall Campground. Wingspan measurement was as pictured. From what I can tell, there are only two Eupithecia species that have this type of wing pattern with basal area mostly white, white head, white thorax (with vertical brown dash at bottom), white tip of abdomen, white chevrons on abdomen, and large dark marks on sides of upper abdomen. Those species are nevadata and ravocostaliata. There are no BugGuide or MPG records of ravocostaliata this far south and the food sources for that species are not likely to be found in the Mojave. However, the Mojave is known for three species of Purshia (Bitterbush), the favored food of E. nevadata. I am not sure why BugGuide images do not currently reflect much in the variation of this species. This moth here probably compares best to a couple of images on MPG (specifically Dick Wilson and Jim Troubridge images) and some Barcode of Life postings.

Note: Since submitting for ID, I have reviewed a publication by Clifford Ferris (2018), and now see that that there are two known subspecies of E. nevadata. They are nevadata and morensata. Of nevadata nevadata, Ferris says on Plate 143 that "...there is considerable variation in coloring and maculation among adults."