Originally described in 2006 as Claytonia ozarkensis, this plant was considered a near-endemic to the Ozarks, being found in Missouri, Arkansas and Oklahoma. Yatskievych et al. (2013) further defined this form and re-described this as C. arkansana. This species is known from only three counties in Arkansas and is classified as G2, or globally imperiled due to its required specialized habitat. C. arkansana is only found on sandstone bluffs and ledges. An interesting adaptation this plant has required to ensure its offspring remain in this required habitat is by negative phototropism of the pedicle after flowering. As the fruits develop, the pedicle turns away from light so that the seed may be dispersed in the cracks and bluff ledges where they need to germinate.
I want to thank Casey Galvin and John Oliver for helping me find this fascinating plant!
Yatskievych, G., R.J. Evans, and C.T. Witsell. 2013. A reevaluation of the Ozark endemic Claytonia ozarkensis (Montiaceae). Phytoneuron 50: 1-11.
A Thousand Acres of Silphiums 
Nice find!