Turtles that have drifted apart way more then 10 million years ago are still able to interbred...they even come fertile. For example Chelonia and Caretta interbreed and they have drifted apart some 50 million years. Other example is a specimen held at a zoo (if Im not mistaken in Germany), that is a cross between a Emydura and a Chelodina. One more thing, aligator snappers and comon snappers have drifted apart way more then 10 million years ago. Fossils of ancient snappers 30 million years ago show already clear differences betwen Chelydra and Macroclemmys body types. I hold my own that the main thing preventing this cross are behavioral differences, not molecular ones.Chances of the two being able to breed is slim to none, the two different genus diverged from each other almost 10 million years ago making them totally different species and DNA testing has shown that its impossible