Found under a rock. I assumed this would be Castianeira, probably C. longipalpa, but the palp was wildly non-Castianeira. The palp is quite unique and matched SONA figure 20.35 very well. (I have a permit to collect in Austin parks.)

The spider was 6mm when I got it but grew to 7mm after eating a cricket. I fed it a cricket about four times its mass. The spider leapt onto the cricket without hesitation and wrestled with it for a while, standing tall on its legs to get on top. During the struggle it kept its palps wide apart and seemingly as far as it could from the cricket.

The spider seemed to have sand ground into its carapace, which I could only get out to a limited extent by bombarding it with drops of water, prior to the above photo shoot. The sand is even difficult to get off scratching at it with a tool in alcohol under a scope.