Farias IP, Hrbek T. (2008 ) wrote: "These clades corresponded to the 'green' and 'blue' groups of Symphysodon aequifasciatus, and to a previously morphologically unrecognized clade from the Xingu River drainage."
I know well, that in lower Rio Xingu region lives completly yellow discus fishes!
Heiko Bleher wrote in his famous book "Bleher`s Discus" - Volume 1, that "... lower Xingu region also harbours an almost quince-yellow variant, which I have also found and which is today seen in the hobby. It is almost perfectly circular discus." There is realy nice photo of this yellow discus on page 239 (English version)!
See also nice yellow Xingu discus here:
http://www.1afische.com/site/shop/image ... u_g021.gif
Is this maybe a new species?