In my opinion, doubtful that it is any Anemone or Pulsatilla(Anemone) patens.
If you look at my photo here
http://nargs.org/smf/index.php...
you'll find an assortment that includes Corydalis, Anemone and Pulsatilla in the seventh column. Click on the image, and it is detailed enough for you to zoom in and see. Count from the left, the seventh column is the one that starts (from the bottom) with the tallest white tag.
You can see that Anemone and Pulsatilla have much broader cotyledons, and are held differently. Indeed, yours may not be Corydalis, though. There are many, I would think, that can look like that at such a young stage.
Other things from the top of my head:
parsley
Adlumia
other Apiaceae (Carrot family)
