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Newly discovered lizard fossils from the Upper Cretaceous Djadochta Formation in the Gobi Desert of Inner Mongolia China, include early iguanids and agamids that are taxonomically and biogeographically important. Two iguanids reported here, Anchaurosaurus gilmorei, gen. et sp. nov. and Xihaina aquilonia, gen. et sp. nov.. document the geologically earliest record of the family from Asia, and extend the fossil record of the group by 11-13 Myr. The geological age and primitive structure of these Cretaceous iguanids, coupled with other material of the same group from the slightly younger Barun Goyot Formation, suggest that the group had a long evolutionary history on ?he northern continents, and hence, challenge the widely accepted South American origin hypothesis of the Iguanidae (sensu late). Three taxa of agamids are documented in the new collection: Mimeosaurus crassus Gilmore, 1943, Priscagama gobiensis Borsuk-Bialynicka and Moody, 1984, and Pleurodontagama aenigmatodes Borsuk-Bialynicka and Moody, 1984. Several well-preserved skulls of M. crassus show a structure that requires a taxonomic revision of this genus. Priscagama and Pleurodontagama are poorly documented. It has been long held that the iguanids and agamids have different centers of origin, and that the two groups have been separated geographically from one another since the beginning of their evolution. With the discoveries of new iguanids and agamids together from the Gobi, it is now dear that the two families were sympatric during their early evolution on the northern continents.