One of such neglected lineages is the family Helodermatidae
(Anguimorpha) encompassing two extant species, the Gila
monster, H. suspectum, and the beaded lizard, H. horridum, the
only lizards with grooved teeth and venom potent enough to kill
human beings. The Gila monster, H. suspectum has a geographical
distribution in southwest USA and northwest Mexico