Well, as of current scientific thought (might/probably will change), sp. 'Atabapo' is a distinct, though closely related, species to H. severus.
Regardless, care should be the same. A bonded pair would work in a 120, though the parrot will need to be moved out as it gets bigger. But while it's growing it should be fine and make for an awesome tank, sp. 'atabapo's tend to be my favorite colored sev.