You're gonna hate me but Xingus can have spots on their fins. 
Here's matubula panaque thread check his pics out there's I think 10 different Xingus plus a tocatins and tapajos 
http://www.plecoplanet.com/forum/showpost.php?p=106772
What you want to check when buying is their teeth that's the best way to tell what it is. 
I've posted the link twice in this thread already that will show you xingu mouths and talks about the differences of each one. Matt dud a wicked job it's worth reading
Best price $250 for 8"-10"TL or $80 for 3"-4"TL but I'm in Ontario 
Unungy on aquabid has a good deal 
His fish are always top notch and he promised to work on his communication 
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