My best guess would be the native, Daucus pusillus (American wild carrot). It is actually the same genus as Daucus carota (Queen Anne's lace), the European and southwest Asian species that has been introduced into North America and it looks very similar to it. Here are more photos of Queen Anne's lace and of American wild carrot (also called Rattlesnake Weed) for comparison's sake. In case that isn't the plant you've seen, here are some other possibilities:
One of the Hymenopappus spp. For instance, Hymenopappus artemisiifolius var. artemisiifolius (Oldplainsman), Hymenopappus scabiosaeus var. corymbosus (Carolina woollywhite) and Hymenopappus tenuifolius (Chalk hill hymenopappus) occur in Travis County.
One of the Valerianella spp. There are three species found in Travis County—Valerianella amarella (Hairy cornsalad), Valerianella radiata (Beaked cornsalad), and Valerianella stenocarpa (Narrowcell cornsalad).
If none of these are the plant you have seen and you do have photos of it, I suggest that you visit our Plant Identification page to find links to several plant identification forums that will accept photos for identification.