Mysterious Yellow Beauty: The 41st Flower of Spring!

[best appreciated at full size against black]

A couple of weeks ago I looked out our downstairs bathroom window and saw something white and round on the ground. "PUFFBALL!!!!" I squealed, and ran out the door with my camera, Tasmanian Devil-style! As I paused between taking pictures, I noticed a tiny yellow blossom right next to me, and turned to take its picture. Little did I know what trouble this flower would be for identification!

Since I took this picture, I've been looking everywhere for confirmation of what kind of flower it is. No luck. In desperation, I pulled the last of it out of the ground today to take pictures of the leaves at the base of the plant, since the flowers have long-since died. I'm going to add the leaves to this post once I get them cleaned up. What a mystery!! I can't find any other flowers like it to compare against either. What a head-scratcher!! If you ever try to identify flowers, you will soon learn how hard it is to tell one flower from another...sometimes the differences can only be seen under a microscope! Sheesh. I'm interested in knowing about the subjects I photograph, but there's definitely a point where I draw the line! :D However, needless to say, if you happen to know what kind of flower this is, I'd love to hear from you! I'm thinking it might be a Draba or a Mustard but I just can't be certain, and it might not even be related!

This image was taken in April, 2012.