Update, July 15, 2006: I've added comparison images of A. nahuana, at the bottom.
Can anyone ID this Argia? - it's from below Lake Balmorhea, Reeves County, Texas on July 08 2006; the coloration was most like A. nahuana but without a forked humeral. I also have another specimen from the same spot that has appendages shaped exactly like the A. nahuana in Westfall and May; this individual shown here has a very different dorsal outline of the paraprocts, and from the oblique view the cerci have a downward projection at the rearmost point, in addition to a small "thumb" on the inner edge:
UPDATE:
Here is a comparison of the odd Argia (on the left) with Argia nahuana Aztec Dancer (on the right) from the same location:
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here is a second nahuana from the same location:  |