Summary[edit] Description: A typical Dudley Bluffs twinpod in full bloom during late-May. The Dudley Bluffs twinpod (Physaria obcordata) are limited or endemic to barren white shale outcrops and specific soil tongues in the Piceance Basin of Rio Blanco County, Colorado. Credit: USFWS. Date: 15 May 2009, 12:56. Source: Dudley Bluffs Twinpod. Author: USFWS Mountain-Prairie.