but the dorso looks like a match...

with ridges for these tumblers, placement, size, and shape are often appear to be more important than exact number. In that respect they appear to be decent match for Tom Murray's scapularis . M. scapularis is supposed to be a 2,2,1 (can be 2+, 2+, 1+). To me, this one looks to be a 2,1,1 (subapical not included), but it's really hard to tell for sure, even from these execellent images.

All the other characteristics fit nicely within Liljeblad's description, several of which (including the ridge counts) he states are "somewhat variable". Other chacteristics include the red-yellow abdominals and anal style (can vary to "nearly black"), the antenae filiform, long, and black with 3/4 basal segments pale redish yellow. "Legs with all femora blackish, tibiae and tarsi more or less reddish yellow." And of course the humeral spots. They appear to fit scapularis well. There's also a hint of a bit of light coloration aft of middle - possibly this is an especially fresh specimen?

I agree the range seems further south than that listed by Lilgeblad. The few southern on-line state lists I could find do not include scapularis, but then they seem under representive of Mordellidae in general.

Lastly, Texas (and FL) has many range-limited Mordellidae not currently represented on BugGuide (including your previous all-black/grey post), but I'd still cast my vote here for scapularis.

See Riley's Lick Creek Park list (1)
Will post enlarged photo or two of dorso. Thanks much!!