It's not easy to distinguish Plains Spadefoots from Mexican Spadefoots. One way to tell them apart is that when handled, Mexican Spadefoots smell like peanuts (!). I just took photos in the road without handling, so I didn't have the opportunity to experience this. Another way to tell them apart is that Plains Spadefoots have a raised bony area between the eyes, called a "boss". This spadefoot seems to have a bump between the eyes, so I think it's a Plains Spadefoot.

Later in the evening, after I had driven across the state line to New Mexico, I saw a few more. This one also seems to have the bony boss, so I think it's a Plains Spadefoot.

Rick McCarthy and I found this weird-looking animal while road cruising a couple of nights later. It appears to be leucistic, which means that it has practically no pigment in its skin. This is similar to but different than being albino. An albino toad would have pink eyes, but this one does not.

This condition makes it much more difficult to identify the species from the photos. There are three spadefoot species in this area: Spea bombifrons, Spea multiplicata, and Scaphiopus couchii. All three have very similar body shapes, and they overlap in size. S. couchii gets bigger than the other two, but this one was of a size where it could have been a medium-sized S. couchii or a full-sized S. bombifrons or S. multiplicata. The shape of the hardened "spades" on the rear legs would distinguish Spea from Scaphiopus, but I didn't know that at the time and so didn't check for that.

The "boss" between the eyes that I mentioned earlier is present in S. bombifrons but not in the other two species. To me and some others who have looked at these photos, that boss appears to be present here (especially in the first photo), but it's not completely clear. So I'm tentatively calling this S. bombifrons. Please send me mail if you have an opinion on the matter!

I had identified these as Mexican Spadefoots, but Caleb Cam on iNaturalist pointed out that a "boss" (raised area between the eyes) is visible in the first photo. That bump distinguishes Spea multiplicata from Spea bombifrons. (I'm assuming that the second individual is the same species as the first since they are extremely similar in appearance and were found close to each other, though the angle of the photo is such that you can't tell whether or not a hard boss is present.)