Wow! I've never seen anything quite like this before. I agree with you in that it is most probably a Laetiporus sp. such as L. sulphureus (chicken in the woods). Any chance you can go back and check it periodically to see if it dvelops further.
The fruiting body has developed and changed considerably since this sighting, The top has become darker, and the lower portions more yellow, more convoluted, fissured and dissected. I have images taken at regular intervals. Is there a facility to enter additional images?
I'll chase that up to try and find the best answer for you. I would have most probably deleted image 3 or 4 and replaced it with an update. Though wait till I get some better information back on it. Can't wait to see these new images!