In comparison with Ibervillea lindheimeri: Cissus on the right, Ibervillea on the left. Last photos is just Cissus.
Seedlings germinated in old flower head
Likely antelopehorn milkweed seeds.
During vegetation surveying for the Wildflower Center's long-term ecological experiment. Seeds germinating out of an old flower head. The only flower heads we found in the area were of Rudbeckia.
@kip_lary obtained some excellent macro shots here: https://www.inaturalist.org/observations/189262123