From what I have observed on earth, this creatures existence was most likely influenced by evolution. Evolution as in survival of the fittest. The evolution that every single man woman and child thought so basic and clear, as to have no need to even make a word "evolution" for it. I have no way at all of even considering whether this is speciation or not, besides the fact speciation had never been observed, yet dogs show a greater variety of characteristics than 2 sets of different species might! From observable facts I see that it is possible this is a transitionary look of this turtle, and it may of evolved from link x to link z,(whatever the species quoted here are) without changing species.
It takes leaps and bounds of faith to be certain this is evolution, (as in speciation.)
You try to be smart, but remember... he who is certain in the least, is also wrong in the least. Knowledge is lessened far more by where you are wrong, than it is heightened by when you are right.