Image of Aristida ternipes

Description:

This mass of one of the "poverty threeawns" was just hypnotic due of the intricate mass of (empty) flowering heads. A close up of the mass as shown in the second photo would make a fabulous--if infuriating--jigsaw puzzle! I only had access to a generalized reference on Sonoran Desert grasses which listed four similar species which occur in the area: A. divaricata, A. hamulosa, A. barbata, and A. ternipes. I'd like to narrow the ID down if possible. I saw this grass at the Gilbert Ray Campground as well as the nearby Arizona Sonoran Desert Museum and in the adjacent Saguaro National Park.