I think you got it Lin. I found a pdf file online called
LIST OF DOMINANT AND COMMON
WETLAND, DUNE AND COASTAL PLANTS
OF THE WETLANDS CENTER PREMISES AND GALVESTON BAY
and Aphanostephus skirrhobasis is one of the first plants listed.
http://www.tamug.edu/seacamp/i...
The first few pictures I found, the leaves didn't match, but others did. I might have something to do with growing conditions.