Black wolves are a different species not specific to the xingu river. I believe hat they have also been found in Peru. There was some talk a few months back that it'd be described as a new species, but I haven't heard if they decided on a name yet. Max out around 18 inches or so. Some say 20-24, but the biggest I remember hearing about was 18. They don't grow very fast, so it'll take a while for it to reach that size. They are pretty active compared to most malas. Very cool wolf to own.