I have always thought that Parsons was the worlds largest Cham Species... This is correct according to the Chams of Madagascar DVD I am addicted to watching daily. But I have seen sellers advertising other species such as Mellers and Oustalets as the worlds largest Cham... What's the Deal? Let's get the record straight here... Cause obviously there is some confusion. Only one species can hold the title of "Largest". I know that the Oustalets Cham are sometimes considered the "longest". I would think that over all body mass and weight would be the deciding factor on "Size".