Its only the spots on the top that are diffrent from mine. Try an take a look around. I know that Miles have postet some pics that look just like yours (and mine).
Sorry, page 147 of Aqualog: Freshwater Rays, P40 Potamotrygon schroederi, pic looks exactly like yours, I don't know what to say. Closer examination of the book I find that nomenclature has a long way to go, to say the least!