Common Evening Primrose (Oenothera biennis)

Went geocaching this afternoon and saw this little wildflower. pretty right?
Options I've come across include: evening primrose
http://lee.ifas.ufl.edu/Hort/GardenPubsAZ/Cutleaf_Evening_Primrose_Oenothera_laciniata.pdf
look at the growth pattern of the flower in the article and the similarity to my specimen. the only thing that differs is the leaf shape (look at the second picture for better leaf clarity)
I'm pretty sure that http://uswildflowers.com/images/full/pict1717.jpg is a match. Leaf shape and what not. I realize why I spotted it, it was beginning to darken outside. And this flower only blooms at the end of the daylight. So this moment in the flower's life it's only been blooming for a minute or so. It was super fresh, but I didn't understand that at the time. :D