If those gars are hybrids, and I am tinking I know where they came from. Last time these gar hybrids were made, they were a cross of a Alligator gar and a Spotted/Florida Gar. Pretty nice fish. Had a couple myself. They dont have as fast a growth rate as the pure gators but grow faster than the spotted/Floridas. They also don't have the aggressive personality towards tank mates like the gator gar does.
About the multiple rows of teet these hybrids will have a sort of incomplete second row of teeth.
those gars look like a crocodile gar, from the shape of the mouth/snout. Which is a cross between a gator gar and a florida gar? Or maybe agator gar and spotted gar.