It is hard to tell from the picture, but what it looks like to me is an incomplete (and malformed) polymerous bloom.
If I am not mistaken, there are 7 stamen in there, with an 8th stamen converted into a full-length petaloid, but not a true, full petal. (This petaloid is at 11:30 in the picture.) So 3 petals, 1 large petaloid.
It also looks like there might be 4 sepals, but they are not symmetrically arranged (at 90 degree intervals).
In the old snail mail poly robins (that I used to belong to) we would call such a critter a "3 x 4 with petaloid" or something like that.
This past summer, I had one seedling (from attempted polymerous breeding) which had blooms that were similarly malformed. In the case of this particular bloom, you can clearly see that there are 5 sepals, 3 petals, 2 (?) petaloids (extra tissue that looks like petaloids as opposed to petals - it looks like there is an anther attached to the one at 7:30), and 6 stamen:
Not exactly something that you want to see show up in your poly patch!
(This summer it is more behaved, in the sense of having symmetrical blooms. Alas, it is only low percentage polymerous, but I am waiting to see if it reblooms and what transpires then.)
