What was the source for your version, and did you make alterations?

I'm sure this song has been treated in previous threads--you've even posted to them previously. The song pops up in nearly every collection of cowboy songs. It's difficult to search because there is no consistency in the horse's name: Platonia, Pattanio, Patonia, ... You pretty much have to search both with and without the L or (first) N, switching A's and O's, and even using double T's. I wouldn't be surprised if there was even a "Pantaloona" and a "Platoonio".

There is no "right". My personal belief, based on the frequency of spellings I've seen, is that the name was originally Platonio/a, derived from Plato[n] rather than Antonio. This is the most central form, and it would be quite natural for Mexican-influenced, less philosophical cowboys to mix it with Antonio.