This plant was found on Mount Magazine elevation 2,500 feet in Arkansas, USA. On 06-01-12. It was on the edge of a cleared and mowed area and heavy woods. It's stems have small prickly thorns and not large ones like some Thistle varieties. The leaves look like those of Crownvetch or fern like. Blooms and seed pods look just like the Thistles. Perhaps someone can ID for me. Thanks!!!