Here’s a split that makes sense.
If you familiar with the split of wood rats into “West of the Colorado River” and “East of the Colorado River” units — a dividing line replicated in other taxa as well — then following that idea, the authors of a paper in the Journal of Mammalogy suggest that “desert shrew” be split at the river as well. (Some references know the former species as “Crawford’s Gray Shrew.”)
The range map for several species in this region of CA, Baja, and SE’n AZ is uploaded now at https://www.mammalwatching.com/wp-content/uploads/desert-shrew-map.pdf
Reading about them is easy. Seeing them, that is a bit trickier.
Charles Hood / firstname.lastname@example.org