Aha! That database of type specimens at Harvard's MCZ is very useful. Using Mike Quinn's checklist for Texas, I was able to get the images linked below:
*Chauliognathus basalis LeConte (and also in the guide)
*Chauliognathus discus discus LeConte
**Chauliognathus discus texanus Fender
*Chauliognathus lewisi lewisi Crotch
*Chauliognathus limbicollis LeConte
*Chauliognathus marginatus (Fabricius)--in the guide here
*Chauliognathus omissus Fall
*Chauliognathus pensylvanicus (Degeer)--in the guide here, of course
*Chauliognathus scutellaris LeConte--type specimen from Texas, apparently
*Chauliognathus transversus Fender
*Chauliognathus werneri Fender

So, from the Texas list we lack images of only these full species:
*Chauliognathus lewisi lewisi
*Chauliognathus transversus
*Chauliognathus werneri
I can't find anything on the web for these species. The match with the image of the type specimen of C. scutellaris is so good, and we can rule out almost all the others on the checklist, I'm willing to put this in a guide, absent contradictory information.

Many thanks!

Good point--it does look close to C. basalis:

I'll have to think about whether to move it to the species level, as a number of species are found in Texas, and I've seen images of few or none of them.