Lucas and Estep (1998) say "key taxa of biochronological value" for Tsagantsabian age are Prodeinodon, Asiatosaurus, Psittacosaurus and Dsungaripterus. But both Prodeinodon and Asiatosaurus are currently indeterminate, so no remains besides the Huhteeg Svita holotypes can be referred to them. Psittacosaurus is said to also be in the younger Khukhtekian sediments,