Strange Parhelion (sundog)

I saw this strange-looking sundog-type phenomenon at about 6.15 this evening.  I had to use a graduated ND filter to try to dull down the sun a bit, which is at the top of the image behind very thin cloud, and I reduced the highlights and whites a bit in Photoshop, otherwise the image is as it came out of the camera.

We see sundogs quite often here, but usually they are just feint rainbow-type effects on one or both sides of the sun.  I have never seen anything quite like this before. 

I have uploaded another image of it, showing the left-hand edge, which is particularly unusual I think, and it is in "Extra photos".